The return of capitalism? Lmao. There was no danger of 'returning' to something they never left. Read literally anything written by Lenin on the NEP. Stalin was literally the revisionist and needed to get rid of all the people who were still loyal to the international revolution or refused to kiss his ass and toe his line. Most of the people given show trials and purged were heroes from the civil war, Lenin's old friends and principled internationalist communists who didn't buy Stalin's BS theories- hundreds of them didn't suddenly turn traitor. Stop getting all your info from Hexbear, Lemmygrad and other meme cesspits and go actually read Marx and Lenin.