

Lucifer dared to question his father and was cast out for eternity and demonized for not blindly obeying. Not surprising he’d be a bit salty about that.
IIRC in the Bible Lucifer only kills one person, versus the millions God kills at a whim, usually for disobeying some bullshit he came up with that he never told anyone about.
Satan really just runs the place for God’s undesirables. Why would you want to worship the largest mass murderer in history in the first place though?
Assuming the stories and parables are true, or even based on any sort of reality, which of course they aren’t.
It is very likely that was intentional and a planned part of the art in the first place given we’re talking about Banksy here. Knowing how they would try to remove it, and planning for that to further the art would totally be part of a Banksy piece.