Those things you mentioned are true, but the overall movement lived on (and in most cases became the status quo under new leadership).
The modern Left in the US has never suffered such a purge. In fact, the meadership of the modern Left does a much better job of NOT despising their own base.
Stalin was every bit the devoted Communist that Trotsky was.
Rohm was not eaten by the political Left, he was devoured by the political Right, one that favored private ownership of business and a national identity as opposed to an propertyless, international one.
I’m not following you on Mao.
Nazis were a leftist party.. centralized, all-powerful state = National Socialist German Workers Party..
Gleichschaltung. was the term that the Nazis used to describe the consolidation of control over all aspects of society..
Forms of Government Explained.
https://www.youtube.com/watch?v=jJEuZrvNYg0
Yuri Bezmenov explained the Four Stages..
https://www.youtube.com/watch?v=bX3EZCVj2XA
Stalin killed many leftists like Trotsky - like one drug cartel boss killing competing drug cartel members . Think the Bloods versus the Crips, etc.
Mao was also a leftist dictator.