Kojima Productions maybe, but its a dev that is pretty much united around Kojima. Without him, what does the company actually offer? I think Sony are better off continuing contract work with them
Plus, why would Kojima even want to sell? He only just got out from under the yoke of Konami, why would he want to give up his independence again so soon to work for a big company again?
Money. Same thing happened with respawn. They left Activision and formed their own studio, but 2 games later they sold it to EA.
Kojima could feel he has the artistic freedom he wants, and job security he needs, to be able to sell, gain a huge amount of cash, and still do what he wants. I'm not saying he should or wants to do this. But just explaining the rationale of why he could sell