Did you read the article... yes, it did mention a change of petroleum prices, but that hardly was the issue. It was contributing to problems but that wasn't the issue.
The problem with American historians is that they don't talk to the people of Venezuela, though he did get some things right.
This was one of the major factor:
"And that was not the only problem the country was facing; Venezuelans began looking back at the tenure of Pérez – who had left office in 1979 – and found evidence of corruption and wasteful spending among individuals, including the paying of relatives to undertake certain contracts."
The nationalizing (socialism) of the oil was also a major problem. Whereas private ownership caused schools, retirement funds, employment and the latest technology implementation, nationalization caused siphoning off of monies, misuse of finances, breakdown of equipment etc.
Then, with year after year of promise and year after year there was graft, theft and self enrichment (much like the pork barrel spending of today and the favoring of those who support those who are elected), graft, theft, off shore accounts and the promises that were never kept, people finally got mad and upset. I would call it Capitalism without a heart.
Certainly, because of the graft, theft and favoritism, the rich got richer at the expense of the poor.
So, in comes Chavez with "take from the rich, give to the poor, I will give you housing, food and I will take care of you" message. (Much like today in the US). After decades people were ripe for the message.
Results? Everybody got poorer along with the rich. Free petroleum for Cuba, Exportation of socialism/communism. And those in charge get richer (including the military).