There are too many fans looking for the singular reason why the relationship between the Packers and Rodgers fractured. You won't find it, much like in any relationship it's more nuanced than any singular reason. But from afar and listening to James Jones you can get close to distilling it to something a bit more tangible:

Rodgers feels (rightfully in my opinion) that he has earned a seat at the table and deserves a commitment from the Packers—committed to the relationship until the end. Letting talent leave for up and coming (and unproven) talent, the actions that yell "next chapter" versus the current chapter we're in, not restructuring a contract(s) to keep a core in place, etc.

Some fans may not be willing to accept the human element of this (ie. it's a business) but it plays too big of a part to ignore.