I wonder what the plan is for the Sooners right now. They are in the middle of a possible championship season. You can't change defensive philosophies at this point, so what change will actually make them better in the middle of this season?
This timing makes sense only if you have given up on the 2018 season or if he has become a clubhouse problem somehow.
Perhaps this is indeed the mindset, not that they would say that publically, of course.
Considering that it appears that we might possibly have multiple unbeatens (one could argue that Bama [or UGA], Clemson, and ND look like virtual certainties at this point, with OSU probably a lock as well) and some more deserving one-loss teams (Bama or UGA, possibly PSU if it runs the table the rest of the way?), maybe OU is looking at the writing on the wall and figuring that this will be another year that the BIG12 doesn't get a team in the playoffs (I have no confidence in WVU).
If that's their thinking, getting rid of Stoops now gives them extra time to mitigate any potential recruiting damage (especially before the early signing period) that might occur if they let him go later. It also puts them ahead of the rest of the country in terms of plucking the best potential candidates off the coaching carousel to be their new DC.