Hosts don't necessarily know all of the events that will bring in crowds.
So they book early for a guaranteed $x. Then if they see that market rates for nearby units rose to n*$x, it makes sense for them to cancel and rebook at that rate.
This happened to me in Boston. I was going to run the marathon and knew that I needed to book way ahead to ensure I could get a decent room, whether hotel or AirBNB. I booked an apartment in Back Bay. Two weeks later, the host realized it was going to be marathon weekend and tried to triple my price. When I refused his offer, he canceled me.
Fortunately, it was still early enough that I was able to book a hotel near the finish line. Unfortunately, that hotel ended up be the host of all of the press and press conferences when someone bombed the finish area.
So they book early for a guaranteed $x. Then if they see that market rates for nearby units rose to n*$x, it makes sense for them to cancel and rebook at that rate.