I mean, the track record is already established, there is zero left to lose on that front.
If it fails, you are back to where you started. If he succeeds, no one remembers anyway.
After reading that article on the Raiders, I am placing a lot less blame on Carroll than before. He could have some left in the tank but that situation sounded like it was untenable.
https://www.essentiallysports.com/nfl-active-news-ravens-sources-john-harbaugh-wasnt-fired-left-ravens-after-refusing-major-staff-changes/
Doesn't sound like this was initially a firing.
I can see the thought process behind the speculation but Harbaugh doesn't seem much like a Tepper head coach, especially after Frank Reich.
He's more likely to sign Chris Foerster(Dolphins former staff coach that was seen snorting cocaine on video while in the facility) after he says he has cleaned up and is now super religious. That's more of a Tepper hire.