Bill Belichick with the Browns faced much more adversity and produced much better results than Dennis Allen with the Raiders. Just about every indicator you look at looks better for Belichick with the Browns than Allen with the Raiders. The whole 'dysfunctional franchise' angle falls apart when you look at the details.

Belichick's worst season with the Browns was his final season when they went 5-11, but that was only after Art Modell announced the team was moving to Baltimore and set their season into chaos and a 1-6 finish after the announcement. Dennis Allen's best season with the Raiders was 4-12, worse than Belichick's worst. But maybe Dennis Allen inherited a worse team? Maybe they continued to struggle after he left because thats what the Raiders do? Except that's not the case, the Raiders were more of just mediocre before and after Allen's tenure, the Browns were worse. Allen inherited an 8-8 team that finished 7-9 the first full season after he left. Both better than any season when Allen ran the team. Compare to Belichick who inherited a 3-13 team that went 4-12 the first full season after he left, both worse than any season he coached. Dennis Allen's teams averaged 4 wins during his tenure vs 7.5 wins immediately before/after. Bill Belichick's Browns teams averaged 7.2 wins during his tenure vs 3.5 wins immediately before/after. Belichick made his teams 3.2 wins better and Allen made his teams 3.5 wins worse. If they both inherited 8-8 teams you would expect Belichick to go 11-5 and Allen 4-12. Allen did inherit an 8-8 team and went 4-12. Belichick inherited a 3-13 team so it took him a few seasons to get to 11-5 and then he fell to 5-11 amid a flurry of rumors that led to 4-5 start ending in an announcement of a move and name change that led to a 1-6 finish.

I hope Allen does great, but realistically he is inheriting a 9-8 team now and based on his coaching record alone, it would be reasonable to expect a 5-12 season, perhaps 4-13 if you account for the 0-4 start before Allen was fired from the Raiders. To succeed, he will need to up his coaching game greatly and take a next step, not be given excuses because he coached the Raiders.