You almost have it. To be more specific, they left because of the ugly, menacing, bullying, trolling, fact-less and truth-less posts made by Trump idol worshipers. They were utterly turned off and totally disgusted by the completely irrational, illogical, and depraved posts made by Trump idol worshipers.
Trump supporters can cheer over that all they want, but those conservatives are still out here, and they are against Trump wining the Presidency more than ever.
The vast majority of the posters on this site have been here long before this election cycle and they still remain. Your logic is flawed.