Ah, yes, back to speculation. So, I'll add a smidgen to your dog pile ...
I think Richt meant for Diaz to be successor at large. I think the Administration thought so, too. I believe he & the administration was taken by surprise when Diaz took the Temple job. Richt was planning on staying through 2023 then retire, leaving Manny with the keys to the kingdom.
When Manny stepped out, Richt likely made the decision to step down in an effort to halt Diaz's departure. Richt chose the Bowl game to be his last on field appearance, which is why he looked so emotional in the press conference. He knew he was leaving, and his last game was a loss that is evidence of how broken his system was. He is also leaving the program on a low note. almost as low as when he took over 3 years ago.
His High points
~ Winning the First Bowl game for the program in 10 years
~ 2 wins over both FSU & Virginia Tech in the same consecutive years
~ beating #3 ranked Notre Dame
~ a Top 3 ranking
His Low points
~ Losing 2 of 3 Bowl appearances in 2 consecutive years
~ Losing 4 games in a row 3 times
~ Following up his most successful season with the most disappointing one
~ Watching the success of the team dwindle knowing it was his Offense that was the failing component
If Diaz turns out to be what Miami needed to helm the ship; then Richt did us a wonderful service providing Miami with the future.
"It is only impossible until it has been accomplished." ... then it becomes standardized ... and then it becomes regulation ...
Success is measured by results; whereas Character is measured through the means by which one achieves those results . . .
It seems the Rapture did come for one worthy soul:
In Memory of Grandpa Howdy