There is nostalgia because the experience was unique for those that experienced it, with no good Silent Hill game in ages.This franchise is nothing but nostalgia and hype because it may possibly be exclusive. If history is any indication, these new titles won't sell much at all. All prior Silent Hill titles combined are under 10 Million.
PT raised hugely the interest of what could have been done in the horror genre to a wider audience. I ve seen people who never played the series, getting themselves informed about previou sgames, wanting it's return because of it.
By design Silent Hill was less likely to be mainstream. There was less gore, less action compared to its competitors like Resident Evil. It's sales numbers dont reflect on how great the first Silent Hill games were, especially 1 and 2.
I am not sure how many units games that rely more on psychological horror sell compared to those that have a lot of blood and action. But I do get the impression that they generally sell significantly less Regardless Silent Hill 2 was a deep experience and is strongly imprinted in people's mind's.
The game is PC and Console Timed Exclusive so we know it is not exclusive to PS5. I am confident that the interest would have been equally strong even if it announced on all systems simultaneously