Bush’s fault...
It kind of is Bush’s fault. I think history will see his biggest mistake to be the failure to get rid of Chavez when Chavez was actually in custody and standing at the airport, about to be shot or exiled to Cuba. Pressure from the US - or at the very least, lack of support - led to his release.
Bush initially supported the Venezuelan forces that had briefly expelled Chavez, but as soon as there was anger from the Dems and left and howls of outrage at the loss of one of their leading darlings, he backed down. This not only allowed Chavez to resume power, and in fact become much more powerful, it abandoned the people who had risked everything to get him out. It also showed that we would do nothing to help, and led to the unopposed spread of radical Marxism to several other countries (Ecuador and Bolivia, particularly) that were actually struggling capitalist democracies at the beginning of Bush’s tenure.