My honest take is that while Mayo wasn't ready the be the HC for the Pats. But the Pats had the most cap space in the NFL in 2024 off season and did not improve their roster AT ALL. Both tackle spots were a mess and they passed on very good WR talent to take mid tier WRs. That defense regressed because they did not try to improve on that front seven and their secondary showed regression.
Mr. Kraft cited regression as his main reason and that defense went from a top unit from 2023 to a bottom unit in 2024. That is regression without question.