Dude, wtf are you talking about? Maybe more so than any other professional sport (sans a Celtics Big 3 or a LeBron/Wade/Bosh situation), NFL teams can turn it around “overnight.”
Football is 80% about the QB, and a good QB turns things around quickly.
I seem to remember there was a team in 2001, coming off a bad season the year before, who started 2001 off 0-2 and then had a change at QB and won the Super Bowl.
Heck, look at Washington this year. One of the worst teams in the league magically turned into an elite team because of an upgrade at QB.