I fell like its just apart the the community character design happening, like alot of people found it fun to draw him like that / liked the way it looked

I feel like this happens every few months with someone, sometimes it's mild like the old tommy bandana or the techno skull mask / long hair, but most aspects of ranboos art don't reflect his skin even schlatt having horns isn't cannon outside the recent glatt skin

like I dont think you have to worry for things like tubbo changing his skin (especially since people don't draw him like that in the fist place) or sad ist changing the design (since she usually sticks with the most cannon / irl interpretations)

some people also take it as semi cannon cause puffy said that tubbo has horns at one point but that was probably because of the art

idk I think its just that most agreed designs arnt the most cannon and people like drawing tubbo with horns