How did Airbnb, as one of the most successful platforms, start?

"If we tried to think of a good idea, we wouldn’t have been able to think of a good idea. You just have to find the solution for a problem in your own life." -Brian Chesky, Co-founder of Airbnb.

I wonder if Brian Chesky ever imagined how successful his venture will become.

The solution slide of the pitch of Airbnb: