Kind of funny, really, considering the history of these companies. In the early days, EA was one of the principle developers to fight back against Nintendo's tyranny. I believe they were planning to go PC-only rather than cave to Nintendo's demands. I guess these two are destined to not get along, even with changes in leadership.
Still, something had to have happened. I'm guessing that they had an agreement in principle but then a dispute over the details. Probably had something to do with the way EA likes to handle DLC and in-game advertising. That was the basis of their dispute with Steam, after all.
After that, I think EA simply decided to cultivate their consumer base on fewer platforms. If you can get the vast majority of your audience on a smaller number of devices, then you're eliminating some of your overhead.
In the end, whatever the reason, it boils down to money.
