If you accept the premise that the Force has discrete Light and Dark sides and also accept that there must be balance in the Force, it’s hard to figure out how a light-side only faction can ever prevail, because prevailing means that you forgot about balance.
Frankly, the Jedi (as established through the movies) are singularly clueless and/or willfully ignorant as to their own religion. It’s one of those things that if you scratch at even a litle (rather than just sitting back and enjoying the ride) makes no sense.
You either let things stay at equilibrium or you disturb the balance knowing that the reaction will always come, since there must be balance over time. Imagine if you knew that giving that homeless guy a piece of bread would mean someone else would go hungry that night. What is the right action? Should the moral person act or not act? It’s like the principle of karma, but made finite—accruing good karma unto yourself would shaft someone else, which would presumably give you bad karma, and so forth.
Stupid ass prophecy about balance. Everything would have been fine if Lucas had kept the whole messiah bit out of SW. Too much Dune on the brain.