It's probably reasonable for him to calculate that Instagram is unlikely to take action against him because his success means free advertising for them. Also,

It's probably reasonable for him to calculate that Instagram is unlikely to take action against him because his success means free advertising for them. Also, I'm not sure how you can claim that "his work stands up as not infringement"; to my knowledge, he hasn't been sued over this so these pieces haven't been put to any legal test.