Santos was working towards a major league job, and he most probably wasn't in the Sox' immediate plans.
As far as some others, that period coming out of the ASB was pretty telling for Thames. Venable went to the press to announce how hitters had to start getting more aggressive, and they exploded out of the break, scoring 7+ in 6 of their first 7 games. That seemed like an open rift between Venable and Thames.
As far as Katz, the bullpen really stumbled in 2024 and 2025. No, he wasn't given an all Star crew to work with, but seemingly normal relievers who had past success were dropping like flies. Hill, Brebbia, Booser - Cannon and Burke took clear steps backwards. Not blaming Katz for those non-successes, but that all looked like a clear cut-off point for Venable to get his own support guys in the dugout.