Every mainstream electronic trend originated underground:

• House music started in Chicago's Black and queer club scene before becoming global pop
• Techno came from Detroit's Black community before European clubs adopted it
• Dubstep was a niche UK bass music scene before Skrillex brought it to arenas
• Drum and bass evolved in London's jungle scene before crossing over
• Lo-fi hip-hop was a small internet community before becoming Spotify's most popular study playlist

The underground is where risks are taken. Mainstream success is when those risks pay off and get adopted by larger audiences. The underground is not opposed to the mainstream — it feeds it.