You can rent monthly on Airbnb. If I can get a house for 1200/month on Airbnb vs what used to be available on Craigslist for 800 or 600 a month, is that Airbnb’s fault, or is it just the market rate now and it happens that Airbnb is the platform de jour ?
My conjecture wasn't that AirBnB is cheaper, but that the price of housing is what the market will bear.
Maybe the fact that a landlord that would usually have to find a new tenant though word of mouth or classified ads can now advertise to a much wider audience has the result of making the landlord more money and making housing more expensive.