I have more questions, because the writers really didn't think this idea through. This may not be a good episode, but it's certainly thought-provoking, albeit for all the wrong reasons.
* Michael doesn't blend in with human society very well. He's weird and off-putting from the beginning. And why doesn't he do a better job covering his tracks, instead of letting Lupin learn that's he's using a deserted mansion? Does he want Lupin and Fujiko to discover who and what he really is?
* Is Fujiko still an atheist? Wouldn't meeting a literal angel be a life-changing experience that would make her re-evaluate her beliefs?
* How will Lupin and Fujiko explain all this to Jigen and Goemon? "Oh yeah, the archangel Michael tried to get us to steal Satan's corpse because God wanted us to, but we noped out. Just another day at the office!"