Sorry guys, I've been at work all day. Here is the true story, but I will setup a little backstory.
My brother is a lifelong Gator fan, and recently had the ability to move to Gainesville for a job. His wife is a surgical nurse at one of the most respected hospitals in Gainesville, and she is highly accomplished at what she does.
Her boss is not only the head of their medical department, he also happens to be on the Board of Directors for the UF Athletics Program.
He also just happened to be one of the first responders to Urbie the night of the supposed "heart attack" incident.
The way he tells the story, is when he and his group responded it was immediately clear that there was no health issues of that nature. Instead, what they found was Urbie and a WHOLE LOT of drugs(cocaine mostly.) Apparently this was a long-term issue that Florida had known of for a while.
Due to this incident, and what had previously happened with Spurrier and Zook, UF did everything they could to save face by allowing Urbie to step down instead of being fired and all of this leaking out. This is also why they went with an incredibly safe hire in Muschump, someone who has never had any kind of disciplinary issues, instead of a really big name that could backfire again.
I know a lot of you won't believe this because it can honestly sound a little far fetched, but my source is very reliable and I personally wouldn't put this out there without being comfortable over it.