I've said this a million times on here (if you want the long, detailed posts with examples and evidence they're searchable):
Wellman has a long track record of being very, very slow to fire coaches (across all sports). He interviews current athletes, he checks all the possible legal and financial ramifications, and he has a list of candidates ready to go.
I genuinely think he thought both [Redacted] and Manning would succeed here. I think he disagreed with Dino on some fundamental issues (tangentially related to basketball) and exercised his power to oust him, having already done all of those things I listed above. I don't think he ever saw Dino as a long term solution, despite the extension.
He's not stupid. He is arrogant and thinks his way is the only way. That he let Buddie run the Clawson search seems promising, but I'd bet anything the final decision was his and his alone.
The reason he's struck out with two basketball coaches in a row, in my opinion, is a combination of bad luck and not taking risks. He saw Bz and Manning as being safe, anodyne picks that would maintain "historical competitiveness" without subjecting the school to the kind of scandals that have rocked college basketball.
This is closest to one of the last possibilities on your list ("he sees the writing on the wall but will wait to season's end to act"). We tend to get a bit delusional about this stuff, but the truth is no billboard, fan campaign, or privacy invasion is going to change his mind. But these things might very well change the minds of big donors and they have his attention.