In Lucas' universe, the US is the Empire and the VC (i.e., communists) is the Rebels.

Ronald Reagan was in LA and was a union leader and a liberal democrat. But he became put off by the communist sentiment and, by 1964, became the most articulate and vocal anti-communist.

So if you look at it from Lucas' point of view, Reagan would be "anti-empire" but then become a prodigy for the empire, before becoming the head of the empire.

That's all. It's not a statement about Reagan or anything else. It's just that in the real conflict that inspired Star Wars, this interesting thing happened that I think could be analogized in an interesting way in the movie.