Communist parties derive their power from popular support from the working classes
Political power flows from the barrel of a gun, not popular support. But of course strict control of News, Education, public discourse, and suppression of criticism really helps with the popular support.
State violence is used against fascists, sabateurs, capitalists, and landlords
as well as the workers
why there was such dramatic improvements
A phenomena that has occurred in plenty of other countries
studied Marxism and taught it in universities, and more
Priests, much like Bolshevik party officials, exist to maintain the system of control over the working class on behalf of their rulers and religion is widely taught in universities just like Marxist-Leninism was.
Marx has some interesting things to say, he should definitely be required reading, but Marxists treat Das Kapital like Christians treat the Bible.