That's the difference. There have been many QBs that have been "one hit wonders" (one season wonders.) There is a list of names.

I remember

Scott Mitchell
Derek Anderson
Mark Rypien
Jay Fielder
Rob Johnson
Steve Beuerline
Elvis Grbac

More recently;
Vince Young
RGIII

And currently happening:
Kyler Murray
Possibly Lamar Jackson

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To me what separates the "one season wonders" is a QBs ability to adjust back. It really takes a commitment at the very least. Confidence is so fragile, but most with confidence are arrogant.

Unlike college and HS, the pros have DCs who have the ability time and talent to study and see a QBs weaknesses. Often times during the time of the heat of a season, they don't have the time to really study and game plan.

In an off-season they will read footsteps. If they are scramblers or running, they will know what side they run that is stronger. How they do on 3 step, 5 step, and 7 step drops. They will adjust and have a game plan the next year.

It's how well a QB ADJUSTS back TO THAT ADJUSMENT that separates the truly great from the ONE HIT WONDERS.

Many times it is because the flash in the pans don't have the discipline that is fueled by humility to adjust back.

Kyler Murray is the perfect example that illustrates my point.