It's demonstrably false that "the best player starts" when it comes to JB's teams.
Now, it is true that the best players almost always get the most minutes. In fact, one can argue that, at times, those players get a few too many minutes, and it harms the development of the bench over the course of a season.
But I've seen too many starters-in-name-only in my time following SU hoops to believe the "best player starts" trope. I mean, just this month we saw "starter" Alan Griffin log minutes of 12, 15, 11 and 13 in the last four games of this season. Clearly JB thought Braswell was the better player, and he logged 27, 25, 29 and 15 minutes over the same 4 games.
Point is, I'm sure there are a lot of factors that went into Kadary's decision. Some we may lay at JB's feet, others not. But we do know that in the last six games of this season Kadary's minutes were 18, 10, 17, 16, 14, 23; while Girard's were 23, 33, 24, 29, 29, 24. So Kadary certainly knew who JB thought was better.