It's a blame game society, isn't it?
The answer? Pete and John brought JA to be the galvanizing piece of a defense that could only have but so many 'elite' pieces due to salary cap limitations and the construct of the team at the time.
He SHOULD have been enough to pull together a unit to the degree the team could make a legit run. And it should have worked. The logic was sound. The extension made sense in the context of the team as it was built and under the assumption that Russ would be Russ, we'd have a running game that was formidable for a long time behind Carson and Penny, and a defense that could be dangerous in spots, if not dominant all the time. And then...
We lost Carson, Penny, and the Russ saga went down. And ultimately, Jamal got hurt. Again, and again. After that, the reason for him being became less obvious. In 2021, after an offseason that saw the Russ era begun to unravel, they shoved JA into a more traditional role, I think, in anticipation for his need to be something quite different after they moved on from Russ and would be in a position to completely reconstruct the defense that he was brought in to simply weld together. That might have worked too. But then he destroyed his quad. So now it is what it is. He's angry and probably beyond disappointed to have thought he was co ing to a situation that would see him part of a championship team, only to be injured the way he has been and for the team to have been through the implosion it has.
I think his character has shown to be too self absorbed and too sensitive to fit with what we are doing anymore.
But to assign blame? There are too many reasons, factors, plots and subplots to try to hang 'blame' on anyone's door. He was brought in for a purpose and that purpose no longer existed for various reasons after his 2nd year here. Arguably, after his first.