The Jets messed up in two ways with Aaron Rodgers:
Last October, Sportico first reported that the Jets declined to purchase insurance on Rodgers' contract to protect the team if he missed games for injury or illness. The Jets missed out on recouping up to $22 million in insurance proceeds by not purchasing one of several policies ranging in price from $1 million to $4 million, per the report.
Not mentioned was the biggest loss the Jets suffered by forgoing insurance, the very reason that [one expert] calls this a tragedy: the corresponding salary cap relief.
The CBA labels insurance proceeds as a "refund from the player," which qualifies the amount as a cap credit for the club for the following season. In the simplest terms, if a player who eats up a significant portion of a club's salary cap misses significant time with injury or illness, a club doesn't have to take it as a total loss, but can recover space for the following year. Plus, insurance premium payments don't count against the salary cap.
(The long article is mostly about the salary cap loophole)