All of those are really easily justifiable.
1. Light a fire to see who grabs the job when both guys stunk (Shesterkin did grab it, which seems inevitable, but the tactic worked).
2. Line rotations: nothing was working.
3. Jack Johnson over Hajek: Vet stabilizer to transition the team to Martin's expectation (it worked).
4. JHS can't count

5. Let the proven player work through his problems (we're seeing the same now with Kreider)
6. Again, nothing was working... including Strome/Panarin
7. You're really talking about less than half of the 45 games they've played that this is the case. Their powerplay has been fine since early March (8th in the league 3/1 to now)... 25 out of 45 games played. On one hand, I felt like he stuck too long with a top unit that wasn't working. On the other hand, that same unit is the one that's working now. So was it a mistake or did his patience pay off? That's all subjective, but "patience paying off" justifies his tactics.
And to be clear: 3, 5, 6, and 7 are all ones where I didn't like what Quinn did. 1 and 2 were ones where my reaction was more "whatever." This is exactly what I'm talking about though. Just because you or I didn't like some of the moves doesn't make them difficult to justify.