I think it was their only option to double down on their decision and give Mazzulla & the players stability.
In saying that, I have always wanted Rick Carlisle, and he should have been signed after Udoka left.
I do think Mazzulla is an extremely intelligent and talented coach, but he is too inexperienced for a team with title aspirations. Inexperienced coaches make inexperienced mistakes and we have seen that over the past 3 seasons.
I like Carlisle as well, but the Celtics did win a championship with Joe as HC not too long ago.