I'm not so sure. If there was a "civil war" among the Sith when the sith Lords turned up and opposed Revan, then if many enough went over the two sides could've had equal forces when they fought, thus most of the ships would be destroyed as it is now...
As for the Star Forge itself, I can think of plenty of things that might have happened to it. Perhaps it still exist in the Revan-dark-side-path, but Revan managed to disable it before he fled, by taking out some vital part of it or something like that, thus the Sith Lords are unable to use the Star Forge now...
I got the impression that through the darkside the Star Forge was somehow alive. If you removed something vital, wouldnt that result in death?