You are giving a very simplistic, and IMO a very inaccurate portrayal of what happened in Season 5.

Scott was the first horseman to be evicted by the opposing alliance. Jase was betrayed by his own alliance (Drew) and was evicted. In other words, Drew abandoned his original alliance and joined the side that you would describe as "the floaters". Given that the horsemen were so vile, the floaters aligned themselves to destroy the dominant alliance (the horsemen). Yes, Drew and Cowboy went on to the finals, but it was Diane who played a crucial role in accomplishing that. Diane betrayed every single person in her own alliance to advance herself (and Drew) further in the game. Drew and Cowboy ended up in the finals by no merit of their own, but because Diane carried them every step of the way, even to her own detriment. But by then, the original horsemen alliance was already defunct.