There really isn’t too much to figure- its simple actually.
The same coaches (Reid, Shannahan, Pederson) and franchises (Eagles, Pats, Niners back in the day) have the magic touch developing QB’s.
Then there are some franchises (Jets, Browns) who spend tons of early draft capital at the position yet suck at developing QB’s
I would put the Packers in there too. They deftly transitioned from one HoFer - Favre - to another in Rodgers. And yesterday when Jordan Love started the opener, he was just the third individual QB to open the season for the Packers... since 1991!
How do you explain that versus teams like the Browns, Bears, Jets, Seattle, and Chargers (last great QB was Dan Fouts, by the time he is done Justin Herbert may be up there too) who can never seem to find a QB?!