Not to continue down the KR rabbit hole, but IMO, it was absolutely JB who "made his choice". I'm not a JG3 basher and I honestly believe as I've said before, in a coupla years we'll read some of the criticisms about him and much like Sr-yr Andy Rautins, we'll wonder what people were thinking.
But it was pretty obvious to anyone watching that Kadary was the better, the purer PG on last year's team. A large majority of the season was spent w/ fans, former players, & media, all asking the same questions: "Why isn't this kid getting more PT"? And the guy who was getting the bulk of time wasn't exactly lighting the world on fire either.
Much like the year before when JB made his choice for Joe over an ineffective Jalen Carey, this past year the same variables were on the table, and JB chose to keep playing JG3. It's speculation of course, but unless more comes to light, I'd wager that's where he lost the young man. And when KR looked at the option of coming back and splitting time next year, he took his ball and went home...literally. Maybe he lost faith or just didn't agree w/ the plan, or just got tired of how things were being done under JB, who knows?
Perhaps due to his famous loyalty or whatever, JB made the choice and decision that a struggling JG3 was a better 1st option than Kadary. We can argue whether he was right or wrong, but he called that shot, no one else. JMHO