Have you watched many Seahawks games this year? Harvin was ok running the smoke and bubble screens and other short to intermediate routes, but wasn't great running his routes downfield. That's pretty much what I remember from his days in Minnesota. Problem is, Seattle loves to take shots downfield via play action. That's not Harvin's strength. Other factors are involved, but for many people that thought Harvin was an unnecessary luxury for Seattle from the start, it makes sense that they would cut their loses now. It was a failed experiment and Schneider was smart enough to move on (though foolish enough to overpay initially). But looking at the metrics, Wilson and the Seahawks were more efficient without Harvin on the field
How Harvin performs with the Jets is anyone's guess. He has the talent, but does he fit their system? He is a unique player, but not necessarily a great WR.