Expanded from an earlier answer of mine

After the victory in the Civil War, the Bolsheviks ended what was termed "War Communism" for what the state called the New Economic Policy (NEP). War Communism had allowed for the Bolsheviks to win the war through a very ruthless control over the economy that nationalized many key sectors, but at significant costs that could not be sustained in peacetime. The destruction of the civil war as well as the Bolsheviks' own inexperience in running a peacetime economy necessitated a strategic retreat on economic matters and the reintroduction of limited markets and a lessening of state control over the economy. For many outside observers, the NEP period appeared to be an enlightened time that showed the promise of the Bolshevik Revolution. But despite these gains, the foundations of the Stalin turn were present in the period of NEP.

NEP was really more of a temporary expedient to the Bolsheviks ruling circles, including Lenin. The cultural innovation of the NEP period and the very fact that NEP coincided with the formal declaration of the USSR imparted to NEP a luster it does not really merit. Many of the basic precepts of Stalinism were established during the NEP era; the state retained control of heavy industry, international trade, and the Communist Party emerged as the hegemonic political party within the Soviet state. Although Lenin suffered a stroke in 1922 that severely restricted his ability to directly intervene with direct policy, he shared the apprehension many other Bolsheviks had about the crass consumerism and social disorder of the NEP era. What survives of Lenin's writings on NEP suggests he wanted a NEP that last several more years or decades, but it was still a temporary way-station to a true socialist society.

The rationale behind adapting NEP was twofold. Firstly, it was to alleviate peasant unrest and prevent famine. Second, it would impart some degree of political stability to let the Soviet state solidify. Once these post-civil war crises had seemingly passed NEP would not survive for long. Not only was NEP ideologically at odds with Bolshevik hard-liners, it also threatened the emerging interest-groups within the Soviet state. NEP's limited acceptance of small scale entrepreneurs and liberalization of agriculture starved the growing Soviet bureaucracy of revenue. The NEP era were lean years for the Red Army to the chagrin of more militant Bolsheviks. Furthermore, there was a growing socioeconomic disparity between the NEPmen and the average Soviet worker. The former could enjoy the new restaurants, dance halls, and sundry "social" amenities (prostitution and abortions skyrocketed during the NEP period) which an honest Soviet proletarian could not partake. All of this fused to create a feeling that NEP was a mistake among both the new state elite and many Bolshevik ideologues. Many of the police police initiatives begun under Stalin's watch such as the reviving the tsarist system of internal passports were initially floated during NEP by Soviet police chiefs as a means to regulate the social instability of the NEP period.

NEP gained a degree of wistfulness with the advent of Stalinism. Some of this was earned. The NEP years were actually quite beneficial for the peasantry. The peasant farmers had to pay taxes, but could market their surpluses for a profit. The stability of NEP also allowed for a degree of access to education for the peasantry and upward social mobility as the Bolsheviks did place a premium on proper class background for access to these institutions. On the cultural front, NEP was a period of experimentation and the avant-garde, most famously in the visual arts and in cinema. The appeal of the Soviet experiment drew in many different artists and intellectuals from around the world and added to the cultural prestige of the USSR. There were also genuine hero cults around Soviet explorers and aviators an their prosaic class backgrounds were one of the sources of their popularity in that it was a sign the Bolsheviks were serious about social leveling. The 1920s were also a period of very strong ethnic nationalism within a Soviet context. Lenin was very forthright in his condemnation of Great Russian chauvinism and the nascent USSR did enact policy to counteract what Lenin described as the tsarist "prison of the peoples." Through the policy of korenzatsiia (indiginization or, as Terry Martin termed it Soviet affirmative action), the Bolsheviks sought to promote native cadres into the CPSU, who in turn promoted local languages and cultural programming. The national sections of the CPSU all sought to square nationality with the new ideals of the Soviet state and this did provide for some popular participation in the state by its non-Russian peoples.

There was also a major discrepancy between intent and the unintended consequences of the Bolsheviks' various policies. This was apparent in its family policy during the NEP period. By the late 1920s, a number of Soviet officials were aghast at both the number of divorces but also the growth of abortions. But this was a family crisis of the Bolsheviks' own making. One of the biggest reforms of family policy in the 1920s was the state's assumption of control over the institution of marriage and the legalization of divorce. This was of course a natural byproduct of assuming control over the Romanov state in which marriage and family policy was in control of the Orthodox Church. The Bolsheviks tended to treat secularization as a given, and in this family policy was no exception. The largely male Bolsheviks for the most part did not care much for the details of family policy and often delegated this work to female Bolsheviks like Alexandra Kollontai. A number of these activists expressed their intention to use Bolshevik family policy as a means for a wider policy of achieving equality between the sexes. This would not be a destruction of the family, but rather a thorough reconstruction of it along Marxist lines. Kollontai would actually argue that this new marriage would be:

a new form of relationship between men and women at comradely and heartfelt union of two free, independent, wage-earning, equal members of communist society.

Kollontai would further assert that traditional marriage, understood as of a piece with the old order, was an archaic remnant of a system of exploitation in the home.

Both her contemporaries and even in some quarters today have taken the statements of Kollontai on the nature of marriage and relations between the sexes as evidence that early Bolshevik regime sought to fundamentally recast gender roles. However, the opinions of these female activists carried relatively little weight within the corridors of power of the emerging Soviet state. The special female sections of the Communist Party, the Zhenotdel set up in 1919 were often the source of mockery by their male colleagues and enjoyed relatively few resources from the state. In a pattern soon to become familiar to other states' legal guarantees of gender equality, rhetoric seldom lived up to reality; marriage might be a secular institution, but Soviet society remained quite patriarchal. Activists, whether in private or in the Zhenotdel, could earn the wrath of the state if they pushed for women's issues too stridently, often earning the charge of "practicing separatism," a claim that carried particular resonance for a generation accustomed to the factionalism of the RSDLP at the turn of the century. Many of the male Bolsheviks' championship of equal rights and sexual freedoms was relatively thin and very much rooted in the prejudices of their time. For example, when the German KPD activist Klara Zetkin appealed to Lenin for permission to organize Hamburg's female prostitutes, Lenin responded with a scathing critique. Lenin argued that prior attention the KPD paid to prostitution was a tactical decision to underscore the moral hypocrisies of bourgeois society. The Soviet leader then shot down any connection between Communism and increased sexual liberalization:

It seems to me that these flourishing sexual theories, which are mainly hypothetical, and often quite arbitrary hypotheses, arise from the personal need to justify personal abnormality or hypertrophy in sexual life before bourgeois morality, and to entreat its patience. This masked respect for bourgeois morality seems to me just as repulsive as poking about in sexual matters. However wild and revolutionary this behavior may be, it is really quite bourgeois. It is, mainly, a hobby of the intellectuals and of the sections nearest to them. There is no place for it in the party, in the class conscious, fighting proletariat.