Soviet optimism wasn't so much a byproduct of post-WW2 euphoria, until after the Stalin death, and Beria removal. The short burst of initial happiness Soviets experience after WW2 was brutally stamped out by Stalin between '45 and '47. Terrified by the idea of the Ivans seeing what life was like in the West, Stalin actually doubled-down on the arrests and trials. Scary stats from historians of that era show that during that period more arrests were down by the secret police than in the bloodiest year of pre-WW2 purge - 1937.
In Spring of '53, Stalin was actually planning mass-scale resettlements of various ethnic minorities. Including a plan to ship all the Jews in the USSR to the Siberian-Korean border to create a proto-Soviet Israel. Thankfully for everyone involved, he croaked. Then, when Beria waltzed in and through he had this in the bag, people held their breath. But, when he got removed by Zhukov and Nikita, everyone in the country took that as a signal that all was going to go well.
Khrushchev brought hope to the whole country. Restrictions were eased. Dissidents were allowed to write, just not a lot. And Gulag system came to an end, albeit unintentionally (long story short, slave labor became economically draining because the cost of feeding the people actually outpaced the product of labor; and the rise of an entire new culture of super-gangs within the labor camps terrified the ever loving crap out of the secret police).
The '50s were hopeful time for the Soviets. There was only one fear - War with United States. It was assumed by most ordinary Soviets that it was a natural thing for the USSR to evolve and outpace USA, but the only roadblock could be war with the irrational fearmongering imperialists around the corner with nuclear weapons.
Yet, if you were to ask people of Russia what period of their country's history they would like to live in - I guarantee you, that by a factor of three to one, they'd wish to live during Brezhnev's era.
Because, you cannot discuss the '50s and the cultural thaw, and all the good things Nikita brought the table in USSR, without talking about the end game. Khrushchev destroyed the Soviet agricultural program with his instance of using corn as a stable crop in Russia, mass upheaval of new construction projects (new apartments were created for the Boomers, but they caused internal problems in the country), ossified the country's military (due to the deal he had to make with the old guys in charge of the army in exchange for the coup), and the overall sense of where is it all going.
The '50s were an interesting time for the Soviets, but it was not a time of fond nostalgia, the way the '50s are for United States. It was chiefly remembered for the giddy sense of relief when Stalin finally kicked the bucket, and the uncertainty Nikita brought. His criticism of the excess of his society made a lot of people uncomfortable. Not just politicians, but everyone who benefited from the purges. The entire infrastructure of the Soviet Union in the '50s was staffed by men and women who got there because their predecessors disappeared one night. They got ahead by not asking questions, and here was a funny bald man who asked questions and made people feel weird about it.
Brezhnev was stagnation, but his was a gentle decay of people laughing at the slogans in private and lauding them in public, a comfortable hypocrisy and good concept of what is going on. The '50s brought waaaay too many questions to the Soviets on average to be considered a happy go lucky time.
