Good old bait and switch.
Besides issuing a prompt refund and hopefully banning the fraudulent host, what exactly is Airbnb supposed to do in such situation?
They operate a platform, not an hotel chain. They have nowhere to actually host you and are in no contractual agreement with the guest to actually get you a place to stay whatsoever. Buyer beware so they say?
I think the ask is that they do these things at a bare minimum; at the moment, it appears they do neither with any reliability.