Revolutions pretty always get pretty messy and cruel as they settle in. (That includes the American one, with the victims being especially the native inhabitants of the country). A big factor in extending that period tends to be the activities of opponents from outside; for example, in the case of Iran there was the terrible war launched by Saddam's Iraq, with encouragement and support from the USA - a war in which millions died.

As for Chavez, he's a populist demagogue, but that's not what makes him unpopular with Washington. And being unpopular in Washington is a major reason why he continues to be a very popular populist demagogue in his own country. That and the fact that his populism involves using oil revenues to improve the lives of the poor people who are the overwhelming majority. Very wise, since they are his power base.