I can only assume the reason these games were exclusive to begin with is they assumed the money offered by Sony would eat any sales they would've had in that time period on other platforms anyway. In their brain, since PC is an evergreen platform, releasing late is not big deal.
Hopefully now they finally learned that IS. Brand AWARENESS is so important right now. There are so many games that exist and they're all fighting for our time and money. This situation will only get worse and worse as time continues to move and more and more games get made.
I won't deny that a lot of Final Fantasy fans are likely to own a PS5, but RPGs like this are just as popular, if not more so now a days, on PC. The market has shifted. PS5 isnt popular in Japan and the majority of people in Japan and other countries playing games on their PS5 are playing... well, the usual suspects. AKA not Japanese Action RPGS.
Let me know if my assessment is off base in anyway. But it's hard to shake this sense that the PS5 has become a bit of modern "dude-bro" console. Where a large portion of users are just playing the same thing, not interested in trying different things. To me that's the only way to explain some of this abysmal attachment rates among even niche first party titles like Demon's Souls. The audience simply isn't here, or at least not a large fraction.