I am afraid a comprehensive answer to the question might vastly exceed the limits of a reasonably timed and sized reply – and, maybe, even end up making things less clear – unless, that is, I am granted the uncommon gifts of extensiveness and clarity.

What I can try, is to provide a vague picture of the process – and to point out a certain angle under which your characterization works, and another one under which it doesn't.

Also, as usual, I am discussing Italian Fascism alone – the one I am more familiar with. And I'll leave any examination of fascism as a more general phenomenon to someone more qualified.

First, in examining the “access to power” of Fascism, we should keep in mind that this is merely a formula under which we summarize a particular perspective for our investigation into the actual process. A question indeed.

This framework – that of examining how Fascism gained access to the “main console” of the State, or more properly, how it managed to grow from a particular, fringe expression of “national radicalism”, into being perceived as a legitimate political force, ready to partake of the institutional forms of the State – is a perfectly legitimate one; and one which has inspired quite a few relevant works on Fascism, even if it was certainly more prominent in the past. To cite a few which come to mind:

Alatri, P. - Le origini del Fascismo, 1956

Valeri, N. - Da Giolitti a Mussolini, 1956

Repaci, A. - La Marcia su Roma, 1963

Catalano, F. - Potere economico e Fascismo, 1964

Tasca, A. - Nascita e avvento del Fascismo, 1965 [first ed. 1938]

Melograni, P. - Gli industriali e Mussolini, 1972

Catalano, F. ; Chieffi, F. - La nascita del Fascismo, 1976

Catalano, F. - Fascismo e piccola borghesia, 1979

Now, I am not saying that the historiography of Fascism has since then moved past an examination of how Fascism managed to forge its relations to the establishment of liberal Italy. It is true that some of these works are more dated than others, and are at times over reliant on a degree of schematicism which has grown less common in more recent years. But that's not the main issue.

The fact that Fascism, first as a movement and then during its transition to Party, managed to provide the Italian bourgeois establishment with a reassuring enough perspective that it came to be viewed as a viable “party of government”, is – in its more basic terms, and schematicism aside – a largely undisputed fact. Indeed, to the point where by itself this phenomenon, which is common to all “parties of government” within authoritarian and democratic systems alike, ceases to tell us anything substantial about Fascism, and about the ways in which the affirmation of Fascism differed from those of any other “party of government”.

The reason why so many authors felt necessary to dedicate their efforts to illustrate this specific process – far from it being especially representative or unique to the phenomenon of Fascism – was the need to dispel the, at the time still persistent, myth of a “fascist revolution” - of a violent conquest of power by means of the “revolutionary action” of Mussolini's March on Rome. From this perspective, a detailed examination of the relations between Fascism and the establishment was a fundamental step in clearing the ground of any possible ambiguity on the matter.

Unfortunately – as mentioned above – this realization, necessary as it was, does not provide us with a far-reaching framework to investigate what Fascism actually was, and how exactly it came to power. In the most basic sense, and without ascribing a literal connotation to the word, one could say that in a bourgeois system every phenomenon is a bourgeois phenomenon, and that every phenomenon which is related to the institutions of the State represents, by that reason alone, a structure of the establishment.

Now, the “establishment” is in itself a very expedient shorthand from a narrative standpoint, exactly because it stands for such a composite and complex articulation of bodies, institutions and structures, that it would be otherwise almost impossible to illustrate adequately. Furthermore, since we are all, more or less, familiar with the general concept, we are inclined to accept it more or less at face value. But – at least for the specific purpose of this question – I would caution against taking the, figuratively effective, image of Fascism being “let in” by the extant powers, as a literal, accurate representation of the historical process.

Which is not to say that there are no circumstances where a – somewhat concrete – threshold between a certain group, or political movement, and “power”, exist – a door to be opened, a gate to be unlocked. But rather that, if not in general at least in this specific instance, the development of Fascism took place “outside of the gate” only in so far and in so much as any “mass movement” within the context of the Italian political system. And indeed, the other mass movements – the socialist and catholic ones – had been (reluctantly) waiting at the door for a few decades when Fascism was, again figuratively, allowed in.

Starting in the 1960s, the examination of the development of Fascism, as a social and cultural phenomenon, until its eventual political affirmation, begun to take precedence over an illustration and clarification of its relations with the establishment. In fact this process (thoroughly represented in De Felice, R. - Mussolini, 1965 to 1997) did lead to a partial revision of of the aforementioned approach, resulting in an attempt to examine Fascism as a mass movement which, organically, becomes “party of government” and then evolves into its dictatorial form – rather then (my own, marked oversimplification) as a “dictatorship movement” which manages to gain power in order to become “dictatorship party”.

Under this perspective, the threshold between movement and power becomes an analysis instrument rather than a feature of the system itself – with De Felice developing his famous dichotomy of “Fascism-movement” and “Fascism-party”. Which should most definitely not lead anyone to assume the “movement” side of Fascism to represent an organism “external” to the establishment. On this point, subsequent analysis have focused more on the particular growth of Fascism and on its specific, local connotations and relations. For instance:

Colarizi, S. - Dopoguerra e fascismo in Puglia (1919-26), 1971

Roveri, A. - Le origini del Fascismo a Ferrara (1919-21), 1974

Roveri, A. - Aspetti della lotta politica dal 1919 al 1926; in Storia dell'Emilia Romagna

Roveri, A. - Considerazioni sul consenso al regime fascista; in Storia dell'Emilia Romagna

A more comprehensive view of the development of Fascism within the general context of social instability due, in part at least, to the inability of the Italian political system to produce a viable alternative to the articulate pattern of relations between central government and local powers (usually summarized under the name of long tenured prime minister Giovanni Giolitti, who established and perfected it during the first decade of the Century) which had represented the establishment's answer to the “crisis of the end of the Century” and had maintained a relative social and political stability during the 1901-11 decade, is given in

Vivarelli, R. - Storia delle origini del Fascismo, 1965-2012

A somewhat parallel approach to the financial side of the crisis of the Italian liberal system in

Forsyth, D. - The Crisis of Liberal Italy, 1993

Speaking of Germany, there were some similar points between the main conservative, right wing parties and the National Socialists. Not in all points, but in some crucial that made a conservative-Nazi alliance feasible.

One of these was re-militarization. The Versailles Treaty, and its provision on making the German armed forces small, was very unpopular among most of the Germans, especially people who voted on the right-wing spectrum. And Hitler was very adamant that he wanted to do away with everything related to Versailles. The decision to increase the armed forces was not unpopular at all among right wing circles, it was celebrated especially after Hitler did away with the S.A. to appease the army, showing that the traditional armed forces of Germany would be the ones to guide remilitarization (at least during the first few years).

Conservative circles were also much more afraid of the economic policy of the far-left than of the far-right. What the Bolsheviks had done in the Soviet Union was nationalize all big property, with aggressive land reform, nationalization of all banks and factories. Some traditional conservatives thought Hitler would be more like Mussolini, with his corporativism, which would lead to government intervention in companies, but to a much lesser degree. Property rights would be (mostly) respected. And they kind of were (at least if you were not a Jew), even if Hitler never actually established corporativism in Germany. Hitler’s economic thinking was much more erratic, and secondary to his main aim, which was rearmament. At the beginning of his rule, for example, Hitler sold the stake the government had on many companies (which had gone bankrupt during the Great Depression, with the Weimar government buying them to keep them afloat). The reason for that? Get funds for rearmament. But Hitler (actually Goering on Hitler’s behalf) later on created a big state-owned company to acquire all the low grade iron ore reserves that the private companies were not exploring. The private steel cartel saw no economic logic in exploring that low grade iron, since they would incur in a loss in doing that, but Hitler saw, because it would make Germany more self-sufficient. Hitler had no actual policy on the desirability of private enterprise or state-owned enterprise. It all depended on whether this helped or not the militarization of Germany. If you were not a Jew, your property would only run the risk of being taken by the state if the state thought it could help in the war effort. Most businessmen got that message and tried to collaborate.

Some conservative factory owners actually left Germany after the nationalization of some of their assets, but most stayed. The Nazi government intervened in economic affairs, but it let the factory owners retain their profits. There was a cap on dividends after 1934 (5% of capital, if I’m not mistaken), but there was at least profit, unlike the Great Depression years. Wages were supposedly frozen and layoffs were supposedly forbidden, but there were ways to get around that, and this was mostly moot. The government expenditure on rearmament was so huge (20% of GDP each year in peacetime basically) that spare capacity soon ceased to exist, and the labor market was actually tight after the first few years. So the businessmen didn’t see the need to lay off workers or negotiate lower wages, they actually wanted to hire more workers and pay them more. They were officially forbidden from doing so, but like I said, there were ways around that (like promotions and other forms of compensations).

Nazi intervention in the economy, in price setting and resource allocation especially, grew as the years went by. This wasn’t desired by most conservative circles, but was tolerated. At first it was similar to what had been instituted in World War One, and German businessmen learned to live with that. Of course this would eventually crash down, Nazi economy wasn’t on a sustainable path at all, and some people saw that (especially those linked to Hjalmar Schacht on the Reichsbank) and tried to “warn” the Fuhrer, who didn’t listen to them.

Another point that the traditional right-wing parties and the Nazis had in common was reuniting Germany. Remilitarization of the Rhineland, and joining German speaking populations from Austria, Czechia and so on to Germany was the interest of the right wing in general. Schacht’s Reichsbank, that I mentioned earlier, for example, congratulated Hitler on achieving what “the Germans” wanted after the Munich agreement, but warned Hitler that he should stop now and that the German economy needed time to readjust. Hitler sacked Schacht, because he didn’t need the man anymore, he had lent a credibility to his regime in the first years (he had worked in the Weimar government, and had been responsible for ending the hyperinflation), but now what they desired was different. Schacht wanted consolidation, Hitler wanted expansion and war, the fuhrer saw the world in much more apocalyptic terms, with the war to create lebensraum and further racial struggle of the Germans soon upon them.

What the traditional conservative parties didn’t want was a war that would lead to defeat. This gets to the point that there were many, many plots to take Hitler out of power, mostly concocted by traditional politicians and army generals. These plots would arise from time to time as Hitler made one of his diplomatic or military gambles to increase territory. They wouldn’t develop further because Hitler basically always won at the beginning of his rule. The conservative circles were afraid that any of these actions would lead to a war against an overwhelming coalition (France, UK, Poland, Czechslovakia, the Soviet Union and the USA) and this would lead to Germany being defeated again. But this coalition never formed (at least in the beginning), Hitler got his way diplomatically, Hitler won. How to oust someone who got what the conservatives wanted? So the coup plots were discarded for a latter day.

And it’s interesting to notice that the plots that went on in Germany (Valkyrie) and Italy (the Grand Fascist Council ousting of Mussolini) were created by right wing people after the great disaster that was Stalingrad. After it was clear that the Axis powers were going to lose (and it was clear to those who noticed it, after Stalingrad they were almost always on the defensive), some traditional right wing plotters tried to do away with the fascist and Nazi leadership. According to what we know they were trying to get a negotiated peace with the Allies.

For the economic data, the source is “The Wages of Destruction: the Making and Breaking of the Nazi Economy” by Alan Tooze (2006).