I don't by that "clean house" crap for the canonical reason Revan activated the mass shadow generator. That quote was by HK, and I believe HK was one of the main supporters after his mindwipe that Revan orchestrated at least the later part of the wars to turn the Jedi to Sith, which is no longer canon.
If we are going to use that for canon evidence, then I can use this:
"When I offered to go with her... she laughed. Then, she attacked me. Revan, at her full power, was more than a match for me. The battle was over quickly - and then she made sure I couldn't follow her, even if I wanted to. She left me there, a broken wreck on the Outer Rim. I vowed that I would never bend knee to another. Any alliances I entered in to would be ones where I was an equal."
-Mandalore
I think there's another option, I think Revan never fell to the dark-side, he felt he need to learn both the dark side and the light side of the force in order to truly combat the sith emperor- all this AFTER he was called/found by vitiate, his cold and ruthless tactics are what 'needed' for their victory over the mandalorians: After Malachor, revan created HK, so that the incident of Malachor would never happen again(he was disgusted by it, so he didn't fall during the mando wars), I think Revan never truly 'fell' I think he felt he - to quote Kreia, needed the contrast, not adherence to a single thing(Light-side) that's my two cents anyway.