Comparing EA and Rovio is silly. Rovio has one product and a couple of other tiny ones. An accurate comparison of Rovio would be to one of EA's development studios, not to all of EA itself.
260 people is a ton for a studio. Even if you look at the really big studios working on the really big titles for EA and Activision, it is usually only a couple hundred people at most. That's to produce things like Battlefield (and it's associated engine, which is quite advanced) not to produce a silly mobile game where you fling birds at pigs.
It sounds like Rovio had way more people than could be useful.