The big publishers' moneymaking franchises have plateaued or declined without anything to replace them, and they're looking to sell their companies before those franchises stop making money. EA and Disney have a partnership via Star Wars that could work out toward making an acquisition or merger more affordable. Disney would probably have a hard time growing by acquiring more television or movie studios, but video games are in a different industry. Disney might see acquiring a giant like EA to be acquiring "experts" at how to actually run a video game business compared to Disney's failed past efforts.

Those are the reasons I can think of. EA was rumored to have hit up every enormous company like this to buy them out, including Apple and Amazon, so it doesn't surprise me that Disney was on that list.