It's like when Sans was revealed in Smash. It didn't matter that he was a Mii Gun Fighter, everyone went bat shit.
No-one really knows why his theme blew up, but it was probably a "why do I hear boss music" thing as a joke that maybe got to far?
But annoyingly most of the Undertale remixes on the internet are just ones of Megolvania, some good, some bad and some for the expanding AU universes(Same as said first, some are good and some are bad).
There are still a lot of remixes of the other songs, but there's always a shit ton of Megalovania. Even it fused with OTHER songs. Sometimes from Deltarune.
It's sometimes hard to find Undertale remixes that aren't megalovania. But there are always some badass remixes of the other songs across the internet, especially Spider Dance and Mad Dummy's theme remix by Retrospecter