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.
Most people are more interested in a quick hype, than anything with good tech. Proof of this statement: look at most altcoins, ICOs, DeFi, NFT and Ordinals. The large majority of it is BS, but because of the hype some people earn a lot of money (and many people no doubt lose money). Add the fact that many "users" don't even want to install their own wallet, and it becomes very difficult to get real users for something that could be good.