I haven't played it, but I got the impression it didn't fizzle out so much as that it simply had one single player campaign and no reason to keep playing once it's finished, and that many people seem to have forgotten games with a finite nr of playing hours like that exist because of the roguelikes, hero shooters, MMORPGs, Minecraft-likes, etc that keep you hooked for as long as possible.
Very true, there is still a loyal following of new game plus players, including myself, holding down the fort but having a linear single player campaign was refreshing.
I have my opinions on the execution quality (or range of execution quality) of the game itself but it still served as my favorite “AAA/AA” major release of 2024.