Partly goalies. Partly injuries. Partly very poor specialty teams play, both PP and PK. Partly depth (think of the names that were on the team last year, but not this year). All of these things were relevant.
Most mostly, it was experience. Even Wayne Gretzky wasn't ready to be "WAYNE GRETZKY!!!" until suddenly...he was. Flat out, they weren't ready yet, last year. And in fairness to management and coaching, they were all but telling us that to our faces, all year long. People who know and understand how these things work saw it, which was why there was such cause for optimism among the smart followers, and such impatience, frustration, and anger among the followers who didn't get it. A lot of people mocked the "it's a process" talk, without understanding that it is, indeed, a process - a process that is now coming to fruition.
I'm a systems guy - it's my education, it's my occupation. It's gratifying beyond words when a plan is made, followed, and comes together successfully. If there are any fans from other cities who are cheering for the Jets, it is this quality that should be most admired.