Does anyone find it incredibly difficult to believe Skrillex mixed and mastered Scary Monsters and Nice Sprites on his own?

Back when I was a young lad, I read he mixed and mastered this album at like 23 years of age. Now I’m an old man, I listen back to this album and realised how incredibly well mixed it is. It’s a mix that would take someone years and years of professional experience day in day out to achieve. So, he is either an absolute genius of a generation, or someone else mixed it. Thoughts?