Mazzulla started as head coach under a difficult situation. The previous coach, liked by the players and successful, had just been fired weeks before the start of the season. The players were blindsided. Assistant coaches tapped out. It was tough.
After the first year, the roster went through some changes but the core was still intact. The core players seemed to buy in. The new additions (Holiday and Porzingis) bought in. A title was won. Last season, the roster again remained largely intact but the team was a playoff fail. Brown was not 100%, Porzingis was about 20%, but the team still should have done better.
This version of the team is going to be a tougher challenge for Mazzulla. Many new pieces to deal with. There will be a lot less winning. More chance of players tuning out or looking for "theirs" vs. sacrificing for the team. It probably won't be pretty which reflects on the coach.
The previous coach was suspended indefinitely once that was found out, just weeks after the NBA Finals loss. The P/R or front office team didn't do a good job handling this and if it was found out that time, they should have just canned him right then and there and started searching for a new, experienced head coach.
Instead, they rolled with an interim coach whom lacked experience that was announced as the HC during All-Star Weekend. Result- get eliminated by a #8 seeded team in the ECF, including 3 home losses in the playoffs. Also had players like Marcus Smart calling out on the coach, Grant Williams acting up etc
The 23-24 season, they picked up guys who were just talented and mostly healthy enough to compete, and also, combined with a fortunate of an easy playoff run beating up banged up teams and the Nuggets being eliminated in the 2nd round.
24-25 season? It was just a carbon copy of the 22-23 run, but I guess somewhat worse.