This is the timeline for all this stuff as well as I've been able to piece it together.
I think when things really started to unravel was after the Minnesota game. It was probably our worst loss this year, and I think the blame game was going strong. I've heard that the coaches really lit into Dylan the week afterward about the things we've all complained about (getting the ball out faster and having better pocket awareness). I'm sure Donnie was hearing from Rhule behind the scenes, too.
Then of course came the USC game and Dylan's injury. I'm sure Dom was feeling pretty frustrated with how things were going. But from the team's perspective, it seems to have been just 'next man up' - they moved on from Dylan without skipping a beat.
Then there was the UCLA game. Dom's temperature had been rising for a while and apparently really boiled over at this point, seeing the offense run so well with Lateef in Dylan's place. He complained that Dylan wasn't getting the development he expected and that Rhule & Holgo called a better game for Lateef than they had been for Dylan. To the former, the coaches said he was playing better than last year, with better stats to back it up. To the latter part, the coaches responded that they called it pretty much the same as they always do, but Dylan changes the play at the line a lot more often than TJ, and some of those changed plays didn't work out and left them in a hole. (Personally, I think Dylan was given too much freedom too soon.)
I think that during the bye week after UCLA, there was still some hope that Dom would calm down and they'd be able to work things out. But from what I've heard, the coaches weren't really that worried one way or the other. They wanted to keep Dylan, but they felt that they could roll with TJ or someone else next year and be alright. Supposedly some players did express concern about Dylan's leadership and attitude, too.
After this, though, Dom really started shopping both Dylan and Dayton around to other schools. Supposedly Rhule got a heads up from at least two other head coaches that this was happening.
So Rhule knows what's going on, and he sets up a little chat with the Raiola family during the bye weekend. Dom apparently asked Nebraska for an NIL raise for both Dayton and Dylan next year to keep them around, and Rhule basically drew a line in the sand and said no, you can come back next year for X dollars, but from now on it’s going to be on our terms, no more special treatment.
I don't know if things were actually finalized at that meeting, but it didn't take long afterward. Dayton decommitted the following Wednesday, ahead of the Penn State game.
There may have still been some slim hope at this point - I don't think the Raiolas had actually received a better offer yet - but I'm sure Rhule was moving on. And by Thanksgiving (ahead of the Iowa game), it was all but official that none of the Raiolas would be returning next year.
I'm a little less sure exactly how Donnie fits into all of this. The impression I get is that Dylan and Donnie were actually not as much of a package deal as a lot of people assumed (and raged about). There was a rumor that Dom and Donnie had a major falling out after the Minnesota game and again after the USC game, with Dom being pissed that Donnie's guys weren't protecting Dylan better. IDK.
(Unless a mod wants to split?)