It sounds like Bud is a lot like Monty, but luckier when they met in the finals. Both are good regular season coach but poor at adjustments that crucial postseason. In regular season, it's more about average performance. CP3 guarantees his team a lower level. But in POs, what works in regular season got special defensive attention that rattles the team. If the coach is stubborn, you get by with the lower bound as far as possible. Our finals' year, we were lucky with injuries to our foes, but were easily dismantled with a slightly more adjusting Bud.
It's noticeable that Grayson Allen never played with Bucks like this season with Suns. So I believe he is not good at developing, unearthing talents of his roster, but focused on winning the easiest way, in the regular season. This is not good trait for Suns which doesn't have much established players aside the current starting 5, due to cap.