DuracellEnergizer said:

It's pretty unlikely that in an entire galaxy, only two Force religions would ever spring up. There should be a countless number of religions and sects in the galaxy, all with their own philosophies on the Force.

But Lucas wanted to dumb down everything, simplify it so he could place undue emphasis on the Jedi/Sith dichotomy.

Actually, Lucas introduced the idea of other Force religions in the Clone Wars.

In an interview, Dave Filoni broke down how Lucas had this idea of what others perceived as magic in other religions in the galaxy was just their own unique way of tapping into the Force.

I thought he had discussed it in one of the commentary videos on StarWars.com but it looks like it must have been in a Forcecast episode.

I highly recommend checking out the accompanying commentary videos for the various Clone Wars episodes. Here's one as an example. They're very insightful on the kinds of things George was up to. A lot of his ideas weren't...that great but every once in a while he'd come up with an interesting concept.

Thankfully, we had Dave there to limit the damage and turn out a great show overall.