Theory about heads exit
I have a theory of why head left. When jons voice changed head got depressed because it couldnt fulfill his needs anymore. Uptil 2004 jons voice were pure eargasm but after this it wasnt the same. Of course this is combined with heads drug use. I refer to a video from 1996 (kill you studio) where head says: "The best singer in the world is in my band"
But still just a theory