They also purchased Sucker Punch, and a lot of Sony studios did grow a low and now have 2 or 3 internal teams. In addition to this, they also had 2nd/3rd party studios like Quantic Dream, ThatGameCompany, Housemarque, Ninja Theory, Queasy Games, Zingagi, Tarsier, Double 11 or Novarama working on Sony exclusive IPs.
To do it gave them a lot of exclusive games, both new and existing internal IPs that never won't move anywhere as did the old 3rd party exclusives from the past, where MS has been relying too much.
Now Molyneux, CliffyB and Bungie left, Epic is not interested on more Gears and IPs like Bioshock, Lost Planet, Dead Rising or Mass Effect were ported elsewhere.
Yes, MS has to hire people to create new studios or teams and maybe to purchase some big 3rd party studios to match Sony's great output of exclusives instead of focusing on moneyhatting 3rd party games that sooner or later go multi.
Now they don't have all these people developing exclusive stuff and in the long term would be more profitable for them.
All this exclusive content really did help PS3, like price drops, OS/PSN improvements to match XBL, multis started to don't suck on PS3, new services like PS Plus.
To make a great comeback MS needs to price drop at least $150 to compensate the difference in horsepower that is more visible than last gen in multis (probably dropping Kinect), to match PS Plus/PS Now/Morpheus and to make a great investment in 1st party studios and internal great IPs (specially new ones) developed by 2nd/3rd party studios. And well, to kick the parity launch thing for the indies to get more love from them.