Ollie's career path is very, very similar to Billy Donovan. The fact that Ollie had a longer NBA career then Donovan because of his leadership ability in the NBA locker room is a huge plus not a minus. Both are over achieving point guards, both played for legendary college coaches and against all odds both played in the NBA, both were then assistant coaches for their former head coach before becoming a head coach.
Larry Brown's career path is also comparable.
You also forgot about John Thompson.
Donovan played one year. One. For Pitino because the team that drafted him waived him. Then he went to work on wall street. Then joined Pitino's staff at UK. He was at UK 5-6 years, then had two as HC at Marshall before getting the Florida job. This is a classic coaching resume. Failed player pays his dues as an assistant and then HC at a lower tier school. This is closer to Calhoun's path (he did have a tryout with the Celtics) than Ollie's.
John Thompson played for the Celtics for two years. He was not a successful NBA player.
Brown is iffy. Played in the ABA, not NBA. Also, despite his time at Davidson, KU and now SMU, I think he's known much more as an NBA coach.
Steve Alford mentioned later, played 4 years in the NBA. Started coaching at Division III I might add.
The point is this, long NBA careers do not generally indicate coaching success or appitude. Quite the opposite. Kevin Ollie is an outlier. It was perfectly reasonable to want to see him demonstrate his coaching ability before allowing him to take his very first head coaching job at one of the top programs in the country on a permanent basis. It was a risk to hire him at all. One I am glad WM decided to take, because I too think he's a unique man and is a perfect fit.