> Can anyone give an overview of what has happened in Venezuela since Maduro took over

Venezuela became more authoritarian and poorer. The oil industry collapsed because of mismanagement and the production of drugs rose. Venezuelans fled to Colombia, Brazil, the U.S., everywhere. The usual stuff for 3rd World dictatorships.

> what the beef is between him and Trump?

The same beef Trump has with everyone that he can blame for anything. Trump just wants a scapegoat for his own incompetence, to blame someone else. He thrives on confrontation. That's why he sends troops to Chicago and L.A. and battleships to the Caribean.