The bigger question here is did you pick the team up from Sim, or was it a human-owned team where the former coach left to a new job and you picked it up in the same jobs process.
If it was Sim-owned, then the game is functioning as intended. Sim teams default back to their original Off/Def, which is the one indicated by the email from the assistant coach when you take the job. Previously, they did as you indicated and ran whatever the Off/Def IQ's delivered the best average grade for, which typically meant they stayed in the setup of the previous human coach.
But I would think the switch back to defaults shouldn't happen until the start of a new season when it is known the program is back in Sim hands, not at the moment where the human coach leaves to move up a division or something and someone else can possibly come in to take over right away.