Because you know dick. What you have said so far can be tracked back to one guy's post saying it was 100% White's decision.
"The most ITK insider on Gator BB I know said that he's gone and it's 100% UF/White's decision. Said he can't give specifics, so I'm not sure what happened, maybe something missed in vetting process."
This is the main thread on the UF boards talking about the Gates situation.
https://247sports.com/college/florida/Board/14/Contents/Basketball-Asst-gone-117688356?Page=4
Basically, if you read the rest of the thread, it looks like Gator nation has no clue either what happened. Here are the more interesting excerpts from my POV if you don't want to browse yourself:
"So basically White was uncomfortable with having an Associate HC, but couldn’t change job titles on the dude so he just let him go? Pretty shady if so."
"Jeez. Does White have the guts to assert himself as the HC and be alpha dog/boss on the court? I'm curious on that. From that telling, it seems he didn't have the chops to assert himself and make Gates understand that he's the boss of Gates. Could be a small reason why he brought his old staff along when coming to UF."
"Seems more like a 'cold feet, not feeling comfortable making it known he's the boss' sort of fire rather than a 'you're not doing your job and you're not good for this team' type of fire. If that report is true, it looks like White was definitely not comfortable having Gates around being an alpha type himself and promptly got rid of him because he couldn't control that sort of situation."
"2 pretty connected posters on TOS, including one of the guys who coached the spring game this year said there was nothing UF/White did wrong in this situation so TIFWIW."
"Two different sources (one short of the three I needed in J school) tell me Gates came in and wanted hands on a few things that were already delegated to Nichols. Nichols is one of the most respected young assistants in the sport. White wanted to compromise on it, and Gates doubled-down, leaving White to wonder if Gates really wanted to be here or just felt it was the next step to being a HC. Those sources each tell me White told Gates to handle the Phenom tournament and a couple of 2020 guys that week while he thought about it. This can be cleared privately and also isolated Gates from 2019 guys with whom we had relationships-- it's why Tre Mann kept his visit on, and was smart as hell "
I think (just guessing) the last quote above, is probably the closest to the truth because it seems to make sense. Based on this, I'm guessing there was a fit issue - Gates had different expectations what role he would be playing and perhaps White decided it was a mistake to give him Associate Head Coach title (especially if it rubbed Nichols, his long time assistant the wrong way), he said he'd have to take it back, and so Gates left on his own accord. Keep in mind also the point (made somewhere in the thread) that Gates initially turned down the offer, and had to be talked into it. Maybe he was sold on the role in a way that White was either unable to deliver or regretted or otherwise determined was not going to work. That would fit into the narrative of both White/UF making the call based on the makeup and chemistry of the staff, and Gates's assertion that he was not fired.