There are always ambitious people who are not happy to be paid as much as everyone else. In capitalism, they start companies or climb career ladders in existing ones. In communism, they join the communist party, where (since the party has totalitarian power over the country) it's trivial for them to just assign unproportionately large share of the pie to themselves - the difficult part is winning at politics game to attain sufficient power within the party. Basically total dysfunction that has nothing to do with productive society - that's why every single one implementation of communism had poor results and lead to people overthrowing it one way or another.