As far as I can tell The Day Before was overhyped early and people bought it because of the marketing. Palworld did some advertising, but the mass adoption appears to be mostly word of mouth that the game is actually fun when it was made available in early access.
That matches what I have seen from people commenting and my personal experience as I don't remember hearing about it before and hopped on because of friends recommending it. Palworld is a word of mouth success like Valheim and for similar reasons of competent styling, smooth gameplay, and survival that isn't punishing the player from the moment the game starts.