I'd say at least 6 times out of 10 it's not the contract thats the issue. You just can't develop QBs or coach O.
Like a lot of these failed QBs at some point were making average starter money and eventually average backup money, and those contracts will quickly turn into like bottom 10 starter if they're of any length. It wasn't the potential contract holding back the team, it was the coaching holding back the QB. I say 6 out of 10 because there's still plenty of true flame outs, but at any given time I think like half the league is just gonna ruin their QB.
Bears have a guy at top who is explicitly not a QB ruiner. The leash is long.