The host is Airbnb's customer, listings are non-exclusive (e.g. VRBO), and switching costs for hosts are low. The hosts bring an extraordinarily valuable asset (real estate) and without the hosts, Airbnb has no business.

You are the hosts' customer. You might argue that without the renter, there is no business, but that's true irrespective of the platform. Those hosts will list somewhere and get renters, as long as there's a market.

Presumably, bad hosts (not Airbnb) would take the hit of offering a poor experience over time, and better hosts would prevail. So, Airbnb's goal is to stay out of that fray and keep as many hosts as possible on their platform in order to capture as much revenue as possible from the good hosts, as well as any revenue available from hosts on the descent.