These comments are extremely misleading at best. The notion that the 1990 Browns season was an anomaly, and the implication that the 1991 Cleveland team was just as good as the Browns teams from the late 80s is flat out factually untrue. Yes, they "were one of the top AFC teams in the five years before Bill" - but that was absolutely no longer the case in 1991.
The Browns run of being a good team was over. The notion that they were good a few years previously and should therefore still be successful defies reality. Based on that theory the Falcons have no excuse for the last two losing seasons, nor do the Eagles for failing to have a double-digit winning season in the same time span - and that any run of success should continue indefinitely as long as the QB remains in place.
I don't know why so many seem to feel it is necessary to say the credit should go to just one (or mostly one), rather than both.
That said, I would like to offer a rebuttal to those who point out Belichick's record in Cleveland as evidence for crediting Brady for the success of the franchise over the last two decades, and minimizing the effect BB had on the dynasty.
For the tl;dr crowd there were three specific circumstances: (a) the cupboard was bare, requiring a full rebuild; (b) Bernie Kosar became completely insubordinate and forced his own removal; and (c) Modell's decision to move to Baltimore became public early in the '95 season, causing an ugly and unprecedented distraction. Testaverde being hurt the same year Kosar anointed himself the HC and OC did not help either.
When Belichick took over in Cleveland the roster was full of older veteran players with declining abilities and big contracts. Similar to what happened with the 2000 Pats, the 1991 Browns were a team transitioning to the future. The '91 club doubled the win total from three to six. Rookies drafted in '91 that would have impactful careers included safety Eric Turner, WR Michael Jackson and DT James Jones.
The team was 5-4 in '92, but wore down at the end to finish 7-9. While it was an improvement over the previous season, it was not as much as one would hope for. The draft was not good, particularly the use of a first round pick on RB Tommy Vardell.
In 1993 Bernie Kosar became insubordinate, far too often freelancing by changing the play calls made by the coaching staff. Kosar refused to reel it in, blatantly refusing to follow BB's decisions. Forced into a corner, Belichick cut Kosar. Vinny Testaverde was going to take over for Kosar but got hurt, and the Browns went 2-7 to end the season with a third string QB, once again finishing 7-9. In retrospect BB perhaps should have had a sit down meeting with other coaches, Kosar, maybe Kosar's agent, perhaps Modell - but the bottom line is that a coach cannot let a player constantly make play call changes like that. A club will never win if a single player believes he is above the team, and is constantly permitted to have the final say.
With Kosar gone, lo and behold the Browns went 11-5 in 1994 with a defense that led the NFL with the fewest points allowed. Belichick and the Browns defeated Parcells and the Patriots in the playoffs, before losing at Pittsburgh.
In 1995 the Browns began the season with a 3-1 record, and 1/4 of the way through the season they were considered to be a serious contender for the Super Bowl. Then word got out about the team moving to Baltimore, and the bottom fell out. The amount of distraction was unprecedented, coupled with an extremely angry rabid fanbase. The Browns lost ten of their final 12 games to finish 5-11.
Consider those factors, plus the circumstances of the 2000 season (see the link to the article in the original post of this thread) - and citing Belichick's career coaching record without Brady is a wreckless, lazy case of taking statistics out of context. Belichick's overall record without Brady is meaningless if one bothers to scratch the surface and objectively look at 1991-95 plus 2000.