This isnt really a great comparison. I dont disagree that this wasnt solving a big problem, but neither was AirBnB. Housing is important, but finding "housing" isnt what they do. They arent finding people apartments to keep them out of the cold, they are finding them alternatives to hotels for when they travel. AirBnB essentially took the vacation home market and opened it up to everybody with a spare bedroom. This is huge, but that is them creating a new market/vastly expanding another. They solved a "problem" people didnt know they had, they didnt provide people with food and shelter.
Have another comparison. I have severe, chronic back pain every single day of my life. I've had a bulging disc in my lower back, L5, for damn near a decade and on many days, it's just about all I can think of. I plan my days around my back pain. I make life choices around my back pain. I want it to go away, very very badly.
So, on a scale of 1-10 in terms of "just how painful is it", where 10/10 = you just severed your femur, I'd rate my back pain a 6/10. I'd rate my inability to find a local venue for an indie flick a 1/10. In other words, my inability to see indie flicks at cool bars around town doesn't even register with my psyche.
It turns out that lots of people have back pain. If I had to guess, probably more people have back pain than want to find a local venue to see indie flicks. I'd rate the back pain market size a 7/10. Not sure on the market size for finding local venues for indie flicks.