A much better analogy would be................ you buy a bunch of unknown junk at auction.
In that junk, are tapes with a guitar player called Sam Smith, that you have never heard of and neither has anybody you know.
You like the music on the tapes, so you punch the players name into Google and nothing comes up.
You make a few copies, people like them, you start to sell them, and then...........................Vivian Maier happens.
This Maloof guy did not start out on some sneaky, criminal plan to rip-off Vivian Maier.
Nobody knew who she was.
Its not like he was making copies of Ansel Adams photos and selling them.
What he eventually did or is doing may or may nor be legal, I have no idea.