I won't feel one ounce of pity for the "investors" who lose their shirts when this bubble finally pops. We should regulate investors almost entirely out of housing. Yes, there is still a need for people with lots of capital to go in and repair dilapidated homes. But we don't need people hoarding homes and renting them out as AirBnbs.
It's somewhat fashionable for well-off people/families to have a vacation home somewhere vacation-y. Before Airbnb, most of those homes just sat vacant for most of the year[0]. Clearly, that's not a great use of that land. Often these sorts of properties would be in pretty desirable locations, and doing it this way would deprive most people the use of that space. Certainly there are still some people who are wealthy…
You are missing a critical issue. Airbnb makes it way more affordable to have this second home, so now many more only-sorta-wealthy people can afford vacation homes while pricing people out of the local housing market.