Chavez actually did quite well in the early years. I'm not sure he nationalized oil but took greater amounts of the revenue in tax and used it for positive things for the people. It went downhill after a while with many of the problems common to communist policy though.
Chavez was corrupt but the people he replaced were also corrupt. Even when Venezuela was "rich", most of the people were poor and felt like they weren't benefiting from it. The US is probably going push Venezuela to that prior state, where the country is rich on paper but most people are struggling, setting up a call for another Chavez. That assumes the US can just waltz into the country and take complete control, which is probably not going to happen.
You always get that last golden egg out when you kill the goose.
He was awful from the start, sending political opponents to prison and transferring oil money to himself and his croneys, but he claimed to be taking from the rich to give to the poor, so the Western left lapped it all up. It took them years to realise what he was actually doing (from the start).