I mean pfu has never been a enthusiast brand, the hhkb is just a product that happens to cater to a lot of enthusiasts with it's layout and switches. There is definetly a reason why they went the route of using mx silents and implementing things such as a trackpoint, mouse buttons and gesture controls, it's far more appealing to the mainstream audience which is their biggest market by far. I think customisability was the biggest factor why there was change (and it probably being cheaper than producing everything for topre switches)
It's really only been quite recent where customising keyboards has really hit the mainstream (probably like 2018-2019) and that has been a huge factor, so it's probably more beneficial for them to switch, plus people are more used to mx nowadays.
Honestly I don't think they need to change the hhkb apart from adding qmk, there doesn't need to be a new one.