I've seen this topic being rehashed a few times now and I think one issue is going somewhat overlooked in the grand scheme of things. The overall importance that an offensive coordinator and scheme has on a football teams success.
I think that almost everyone by now should realize the trend of hiring young coaches in football. More importantly, young, offensive coaches are being hired at a very high rate. Here is why:
As everyone should have seen by now, offensive schemes are a lot more complex than they were 20 years ago and there are clearly offensive schemes that create wins for football teams. For an in-house example, the 2015 Ohio State football team, returned almost everyone besides their young and smart offensive coordinator. That is very clearly where that team failed and I don't even think that its close.
Let's talk about another example with an unrelated team. Just 3 years ago, the Falcons had a 28-3 lead on the Patriots in the Super Bowl with one of, if not, the most efficient offenses in NFL history. This team was led by Julio Jones, Matt Ryan, Mohammed Sanu, Devonta Freeman, and Austin Hooper. Sure this team has lost players like Taylor Gabriel and Tevin Coleman, but they also added new WR2 Calvin Ridley. This team basically did not change besides losing young offensive coordinator Kyle Shanahan. Without Shanahan, this offense went from scoring 33.8 points per game to 22.1 points per game the year after. 33.8 was over 4 points more than the second-best team. This team was LOST without their young, offensive coordinator.
There are plenty of examples of these coaches leaving and the teams falling apart at the seams. Nevermind the overall risk of having these guys on your coaching staff when every single team wants. Regardless of what happened, Ryan Day is not Ohio State's offensive coordinator after last season barring a significant raise and a promise that he IS the guy when Urban steps down, similar to what we saw the Patriots do something similar with Josh McDaniels last season.
Guys like Garrett Wilson and Justin Fields came here because Ryan Day is here and there are other guys like Jack Miller that have implied the same thing. Although Urban is an all-star recruiter, I think that losing Urban and keeping Day was a bigger win in current recruiting because it really didn't rock the boat and now every recruit is confident in the staff being here for a long time. While with Urban, maybe we never have to deal with Paris flirting around and maybe Bryan Bresee and Elias Ricks are in the class, but I think everyone is very comfortable with the current class and I think that moving forward having an elite offensive-minded, young head coach is the best thing that you can have when recruiting against the likes of Oklahoma, Alabama, and Clemson for dynamic offensive recruits like we were all over during this cycle.
I think that Urban knows these things and knew it was in the best interest of the team to let Day take over and transfer almost all team properties to him without any feathers being ruffled. Urban has even hinted at the fact that he would not have left if he could not leave the program to Day, which really tells the story to me.