Omg kinda same for me.
I was in the fandom a long time ago, then I at some point forbid. More than seven years passed and one day I find this masterpiece while i was looking for IFs... Months passed and now I'm writting this next to my little Sans plushie, with a (not complete yet) Ralsei cosplay in the closet. Yes, The domino effect was so strong that in addition to returning to the Undertale fandom, I also entered the Deltarune one.
Thanks to this game
Kinda incredible