I think that the problem is that Grin had bad marketing / business development. Many people never really warmed up to Grin.
Truth be told, it's going to be VERY DIFFICULT to create an alternative SoV/payments cryptocurrency (besides stablecoins) that could rival bitcoin, even with a project with good marketing/bizdev. Even those with good technical fundamentals like Monero/Grin will simply just slowly but surely die in terms of attention.