NFL teams get more or less trapped by the fact that only a certain finite number of quarterbacks in the league can lead a team to the playoffs, and end up hitching their whole franchise to fool's gold.
I'm guessing the correct (ie. game theory optimized) GM strategy is to continue seeking elite QBs until you find one, but due to impatient ownership and fans the front offices are incentivized to keep trying to hit 10 wins each season and preserve their jobs. And so you end up in cap hell with a QB who's kinda vaguely top 10 or top 12 and won't get you over the hump.