Remember counterculture isn’t exclusive to left wingers. Just look at how the skinhead culture got co-opted by Nazis. It used to be a subculture of the British working class leftist youths. But because it was an anti-establishment counterculture it also attracted right wingers. Same with how many hippies or wellness moms became supporters of fascists in many countries.

So not very surprising that your goth friend became a Trumpist. The anti-establishment veneer of the right is very alluring for some non-conformists.