Whilst I would be wary of saying AirBnB is the main cause (more likely it's a big one but not the only one), keep in mind that when realestate prices go up in major cities, that pushes out people who go to cheaper places, pushing prices up in those places which in turn might push some out from those places and into even cheaper places.
So housing bubbles centered in main cities do naturally spread out from there to places were the original causes of the bubble are not present.
I literally said 2FA over SMS is not secure because of weaknesses in the GSM protocol.
It's still more secure than username + password alone, but that's it.