You can't put yourself in his position, mate. Not defending him, but the pressure he is constantly under from us lot is enormous. Has been for years and in that sense, I can't really blame him for wanting a break.
I suspect there are many reasons that Ross is leaving. I also believe losing his place in the England team might have played a part, maybe he thinks playing for a bigger club will get him back in it.
That said, think he's better off sitting put. It's hard to tell now, but nobody wants Ross to succeed as much as us Evertonians.