Occam's Razor suggests it's much, much more likely that the team struggled last season because . . .
a.) they lost the GOAT QB in the offseason
b.) the team did not have a thorough and complete offseason program
c.) the team lost: Cannon, Hightower, Chung, Bolden, and Lee due to COVID opt-outs
d.) following a promising start, the team lost several players, including their starting QB, due to COVID
e.) the team had multiple games rescheduled due to COVID
. . . rather than Belichick losing his coaching ability overnight at the age of 68.