They do it in a sneaky way, lots of cliche meme's that get shared and shared. Also when Miley Cyrus wore one of their shirts they got a pretty big bump.
They really don't have that many meme's posted in ratio to their own content posts which still get a lot of attention. I might not care for the music but these guys know how to run their social media.
I noticed that whole Miley Cyrus thing, guaranteed they made a shit ton from that print.
Edit: all the meme content is photoshopped to promote their material too. That's smart.