What always gets me with this story is Couchsurfing, which had proved people were willing to host strangers years before Airbnb launched. I'm not sure why so many investors missed this data point.
But CouchSurfing didn't prove there was a profitable business there. And Airbnb is basically proof of that. If Airbnb stuck with the "stay in a shared room with strangers" approach they also wouldn't have figured out how to make money. As other commenters have pointed out, they shifted to a wholesale vacation rental model (ie HomeAway and VRBO) and that changed everything. They got the benefit of sticking to the "sharing" narrative while making money from the pure vacation rental market.
CouchSurfing did prove that there was a market out there waiting to be tapped though. AirBnB were able to capitalise on it.
Couchsurfing is mostly relying on trust. I've couchsurfed quite a bit (stopped since Airbnb I must say) and every time, people were the sweetest. But that's a good enough situation for backpackers, Airbnb has nailed down the cheap hotel-level hospitality.