Butler made a pro bowl. Belichick thought he was good enough to play nearly 100% of the defensive snaps for 3 years. Brady said he was a good player and would have made a difference in SB 52. Butler started every game for the Titans this season and he played 97% of the defensive snaps. He led the Titans in INT's. He's a good player.
Butler was a much better player than Eric Rowe, Johnson Bademosi and Jordan Richards. All three sucked on literally every snaps in SB 52. That's a combined 98 snaps of awful play while a better option stood on the the sideline in uniform. There's no defending the manner in which Belichick handled this situation.
1) If Butler violated a team rule in such an egregious manner then he should NOT have been in uniform, on the sideline, and playing on special teams. Belichick should have had Butler Inactive for the game and not at the stadium. And give me any bullsh*t about Belichick was "doing right by the player" because that's not consistent with doing what's in the best interest of the team. If Butler did anything obviously bad (like striking a teammate or coach) leading up to the Super Bowl then he should have been Inactive. Under that scenario, f*ck him, and his free agency market, the team had a Super Bowl to win.
2) If Butler was deemed well enough to suit up (which he was so the illness excuse is out) but not effective enough to play over Rowe, Bademosi and Richards (due to a poor week of practice or whatever), then that evaluation should have been discounted as soon as it was apparent Rowe, Bademosi and Richards were getting torched in pass coverage and they were embarrassingly missing tackles. It should have crossed Belichick's mind that perhaps this player in uniform that played 100% of the defensive snaps in the divisional round and conference championship game may have been worth a look on at least one or two plays when it was blatantly obvious the alternatives were f*cking up the game.
Belichick lost that Super Bowl with one inexplicable decision. Making such a poor decision of that magnitude is inexcusable for an alleged GOAT of coaching. Add to that his pitiful handling of the Brady situation and his legacy is taking a significant hit.