You are almost right which your reference said. Oil price was the problem and Chaves was the solution and Chaves was a Socialist and just went too far. Then he died and they got Maduro who, I think, was simply not qualified and has proved that (he was also a Socialist). Going too far as one of the serious diseases of politics. We are getting a bit of experience in this, right now (as far as I am concerned). Once a politician takes a stand, especially a popular one with some true believers, the ride begins. Trump tried that and failed (but he is still trying).

Here is another link: https://www.bbc.com/news/world-latin-america-48121148