I feel like Sony has been making these kinds of purchases (studios already working with them almost/entirely exclusively) as more of a prevention of Microsoft buying them up. It's a weird opposite: When Microsoft purchases a studio, it feels like it is expanding with additional exclusive content, whereas when Sony purchases a studio nothing really changes as these studios already were focused on making Sony exclusives. I'm not criticizing anything, just pointing out that Sony is more on the defense from my perspective. Why else would Sony buy up a studio that was already making exclusives for them if not to prevent someone from buying them up that would prevent their games from being on PlayStation? Microsoft is really the only major threat there. I doubt Sony would care if a third party company had bought out Insomniac, Firesprite, or any other studio they've obtained in recent years because then they could still arrange for those studios to make exclusive games for them. The only one that is threatening the status quo is Microsoft, so Sony seems to be on the defense by locking down these pseudo-independent studios and making them first party studios. Obviously my view is based on more of a general view of their purchases and not all-encompassing.
For context about this studio, here are games they made:
Game we know they are working on:
Theaters of War game mode for Star Citizen (a game that will no doubt release for the PS10, XboxOneTwoThree, and SViwtch.
Buying "2nd parties" is precisely why Sony's acquisitions aren't frowned upon. The harm done to non Playstation consumers is minimal. Sony get the benefit of expanding and future proofing some of their IP's without concerns over the availability of the developers associated with these IP's.
Insomniac's purchase in particular was a smart move to keep Spider-Man locked to their platforms for the time being, as Marvel wouldn't want to soon risk leaving the only developers to have ever made a hugely successful Spider-Man game.
Funding 2nd parties and helping them make a name for themselves does come at the risk of having a 3rd party purchase or "rent" them for their own projects later on. Acquiring studios gives them more control, and eliminates a number of potential problems (including but not limited to Microsoft buying them).
Makes sense for them to do it. Definetly a preventitive move. I just doubt Sony would be buying some of the studios they have bought had Microsoft not gone on a spending spree. Some of them they would have bought either way, I suspect, but others were dependent on this climate we find ourselves in I think.