It's about the power
As with Chavez in Venezuela, the power and access to the wealth is what matters. If the nationalized companies can't deliver product to the people, tough.
The goal is to get a grip on things people need, and turn them into state monopolies. Then the people are pretty much in thrall to the state. Why do you think leftists have been hot to nationalize health care for years?
A mistake I made for a long time was assuming places like North Korea were failed collectivist states. I was looking at it from the point of view of the people, not the leadership.