Most all of Sony's studios were either homegrown or they were 2nd party/exclusive relationships that they developed before buying them. Just a few examples...
Naughty Dog: Crash Bandicoot 1-3 and Crash Team Racing (all exclusives funded by Sony), then purchased by Sony.
Sucker Punch: Sly Cooper 1-3 and Infamous 1 (all exclusives funded by Sony), then purchased by Sony.
Insomniac: Spyro 1-3, 11 Ratchet & Clank games, 3 Resistance games, and Spiderman (all exclusives funded by Sony), then purchased by Sony. They even went off and worked with Microsoft on an exclusive (Sunset Overdrive) but ended up coming back to Sony.
Comparing how Sony cultivated their 1st party studios to what Microsoft has done is absurd. Also it's worth noting that in this case, they're attempting to buy one of the largest publishers in the world. That's just a bit different than buying the team that made Crash Bandicoot. Microsoft has been buying up studios -- and publishers -- left and right, but if you look at the actual output of their studios (not including games that were already well into development before acquisition), it's obvious that they have not been good at managing their studios and their IP. Just look at Halo alone.