The whole "if you die in the game you die in real life" premise is just enduringly popular. There were other anime similar but the very broad MMO game tropes made it accessible, especially to Western audiences where Demon Slayer is very Japanese. I don't know anyone who likes SAO beyond the first half of the first season but what is remembered is iconic. It's set in the very near future so it's more relatable (you could be Kirito, you will never be Tanjiro) and has always been used as the standard for what VR gaming could be.