To not be left in a tough situation.The problem of losing Japan is more than simply not selling games there. Alot, if not half, of the biggest games of the industry comes from there. So if you are Sony and you are trying to convince a dev to develop a game for your system, it would be a harder sell because making a PS5 game instead of just aiming for Switch( developing for just one system is cheaper and easier than two) would mean potentially losing anywhere from 20% to 50% of your audience, because the presence of said game would be nonexistant if the PS5 keeps selling like this. Hell, Square is already doing this.Even if much later, they ported Octopath to Xbox(or just gamepass?) rather than PS4 or 5.And thats especially true for smaller devs.
But its more than that. Having lost Japamn, Sony probably will need to pay more for timed exclusives like FF or MH because companies like Square and Capcom will want their potential loses on Japan to be recouped, since those loses would steem directly from being tied to a console with zero presence in Japan.
And just because you are making a game that has more of a japanese focus, doesnt mean that it wont do well elsewhere.MH was a franchise that did well mostly on Japan, and look at it now. The same goes for Xenoblade Tales Of, Persona, (probably) SMT, etc. The problem with Japan Studio is that their output were not that great, and the ones that were did find some success, like Astrobot. So "all" Sony has to do is build a good team that makes stuff of good quality, and its not just outright weird or too experimental.
An acquisition would indeed be a way to go about doing this, though I would personally hope it doesnt happen, as I personally dont like it.