I also think Maduro was given up by his own. I highly suspect some of his closest buddies got scared by the US force demo in the Caribbean and started to cooperate with them.
Not the first case in the history of US clients. This book I talk about here  >>/54224/ (and many following posts in that thread) tells cases when US military force was mobilized against some unwanted dictator, they did a little bombing and the dictator's own thought better.
Basically they threat with invasion.
I might try to find the specific case.