I apologize if this sounds rambling and disconnected, there's a lot to this. The take home is that authoritarianism is very often a product of governments that assume power through violence, such as a bloody coup or a years-long civil war. Socialist states don't have a monopoly on violent revolutions, nor a monopoly on authoritarianism, but it's also a common denominator in how major socialist states assume power, lets explore this.

Lets set the ideological component aside for the moment and look at governance through the lens of revolution. A revolution itself is an extrajudicial and often violent overthrow of the existing government for a new one through a number of methods, with each method having an effect on its ability to govern. This can be accomplished on a scale from least (A coup d'etat where a leader/cabinet are deposed/arrested and a new one assumes office) to most bloody (a years-long civil war). Depending on how the administration came to power, there are immediate issues with governing that start with legitimacy. A government that assumes power through extrajudicial means faces the first problem in governing with the population's willingness/consent to be governed by the new administration.

A population that rejects the new administration becomes more likely to resist and organize against the new administration, while popular support for the new administration, or more commonly, hatred for the old regime can lend legitimacy to the new government and facilitate a more peaceful ascent to power. A government with little legitimacy to actually be in power will be more likely to resort to authoritarian practices as a way to preserve itself initially and eventually justify its position in power. If an authoritative government gains control of food production/distribution for instance, legitimacy among the people is generated as the administration is now the authority distributing food, and to undo it through resistance will only lead to more instability. The Bolsheviks used such grain and land seizures to this effect when consolidating control of Russia by positioning itself as the provider of grain to the people, lending legitimacy to itself as a governing body. Don't bite the hand that feeds you, after all.

Aside from internal consent to be governed, there's also the other side of the coin; whether the international community accepts or rejects the new administration, and what lengths will other nations go to fulfill their own interests. Revolutionary governments can either rise through support and sponsorship through outside powers in order to usher in an administration more agreeable to their interests, or rise to reject the interests of foreign players. The United States achieved its independence in large part through the international support of France, and to a lesser extent Spain in order to create a political counterweight to British power in North America. The Russian Revolution came about in minor part to secure German interests in removing Russia from World War I, and faced much more immense opposition from the Entente who were intent to keep Russia in the war. The Soviet Union had the disadvantage of having comparatively little foreign support and immense foreign opposition, facing incursions/invasions from nearly every Entente power in order to restore a pro-Entente administration. Faced with such political opposition, authoritarian measures are often seen as necessary by the administration in order to avoid collapse. The Red Army succeeded in defeating the more disorganized White Armies and driving out Entente detachments, lending credence that the authoritarian measures used to keep the Red Army supplied and organized through equipment/food seizures and forced conscription was the reason for the new administration's survival in the face of powerful opposition.

Now lets put ideology back in and get back to legitimacy. Marxist theorists conjecture that communist governments receive their legitimacy through their representation of the working class, the proletariat. That its the will of the working class to break their chains and unseat the bourgeois who have been oppressing the collective majority. Leon Trotsky took this source of legitimacy to its limit in assuming that as the Red Army advanced across international borders, the working class of foreign nations will flock to the Red Army's banner in areas such as Poland and the Baltics. Trotsky was wrong and faced stiff opposition from the national armies of newly formed nations like Poland and Finland, as well as from the opposing White armies and other opposition armies across the former Russian Empire. Where Marxist theory failed to give the popular legitimacy Lenin and the Bolshevik's sought, authoritarian measures such as the previously mentioned seizure of food distribution stepped in to give it instead. Also, if you are to read Lenin's The State and Revolution, you'll be one to think that Socialist states are predisposed to use authoritarian means in order to achieve Communism. After all, Lenin himself asserts such means as necessary in order to achieve communism through the transitory period called the Dictatorship of the Proletariat, where the means of production are forcibly seized from the bourgeois and operated by the common proletariat.

Lets also turn back to the foreign angle and tackle the fact that socialist governments faced much more external opposition from abroad. This is where your question of survivorship bias comes in. It's true that the Soviet Union and China both had common themes in facing intense foreign opposition to their administrations assuming power, and the authoritative measures ushered in by both contributed in their eventual victories and establishments as socialist states. As time passed and foreign powers began to accept that these socialist states were here to stay however, the socialist states weren't beyond rapprochement by capitalist powers who were willing to play ball with the new administrations. After WWII in particular, a Soviet victory over Nazi Germany solidified the idea that the Soviets were here to stay, and as the decades passed, Western and Eastern economies began to do business, especially during the détente era as the Soviet Union became a primary energy supplier to Western Europe in the form of hydrocarbons. What was once a state that arose out of bitter resistance to capitalism eventually adopted a policy of coexistence during the Brezhnev era, as the revolutionary ideals of Lenin were eventually sidelined in favor of pragmatic politics, which was also mirrored in China after the death of Mao and the rise of Deng Xiaoping as a party more willing to deal with western capitalism.

There is something to your idea of socialist states authoritativeness and "survivorship bias" in the face of foreign opposition, but the authoritative approach is also coupled with inherent flaws in Marxist philosophy and the legitimacy of socialist states to govern their internal population. Socialist states often had to fight foreign powers such as the Entente and Nazi Germany, but also their own internal population who resisted socialist rule such as the Russian Whites and Chinese Nationalists.

This isn't a traditional source list per say, but more of a further reading, I suggest looking into these:

International Relations and Political Philosophy by Martin Wight

Marxism in Power: the Rise and Fall of a Doctrine by Michael Kort

The State and Revolution by Vladimir Lenin

Political Legitimacy and the State by Rodney Barker