This is a very interesting move for a few reasons. I had an article sitting unfinished that was going to tackle the game's industry acquisitions but the thing I expected Nintendo (and Sony) to do is make defensive acquisitions. Insomnica was one of these as, like Next Level Games, they had no problem working with Sony and being independent. But Sony bought them up. Right now, you have a lot of big fish looking at video game companies. Microsoft has been pretty direct with this and has also purchased a studio away from Nintendo. With Luigi's Mansion doing so well, they expected they they couldn't afford to lose them.
On the "Nintendo being conservative" part, that was more of an Iwata thing. Yamauchi had no reservations about buying up companies. That's how we got Retro Studios. They also purchased stakes in Rare, Factor 5 and Silicon Knights. They also owned Brownie Brown (now 1-Up Studios). They also purchased HAL for a while (which is how Iwata came on board). Nintendo's acquisitions slowed when Iwata took over. Monolith was only acquired as part of a failed deal to merge with Bandai Namco. The new president has only been around for less than 3 years (started in 2018). Nintendo is also cash rich right now, and they may make other moves.
Wonderful news...buy Platinum now
I get the impression Platinum would much prefer to stay independent, to the point where they reacquired and published a Nintendo IP, even if their financial stability is questionable. At the very least, Platinum currently has of contracts and commitments with other companies, no?
That's kind of Platinum's problem: they need to be bought out but what to play make-believe. On the issue of contract, the only companies that will work with them are Nintendo and Square. Everyone else dropped them (Activision, Cygames, Konami, Sega). This self-publish ploy probably wont work since they have no experience doing it and their games don't do that well. Wonderful 101 is a good reason why it wont work. It doesn't help they are clearly having development problems (remember Babylon Fall that was suppose to come out in 2019 OPPS I mean 2020 OPPPPS I mean 2021). They would be perfect for Nintendo since, despite low sales, Nintendo will take the lower profits to help build the system's profile. Mature games and action games are not in Nintendo's wheel house.
I could see a Nintendo purchase in the future, but this would be after the self publishing goes bust. I don't have any faith in Kamiya's new game.