Their point is probably that Airbnb did not execute anything particularly well and its usefulness is because of scale, not in spite of it. The contrasting examp

Their point is probably that Airbnb did not execute anything particularly well and its usefulness is because of scale, not in spite of it. The contrasting example would be Google, where even before it was popular was superior because of better execution (better search algorithms). Consider a hypothetical p2p car renting company (not Uber). With a few thousand users it probably wouldn’t be that useful as a service, but if 80% of the worlds population had their cars available on it the service would be incredibly useful, despite the core idea existing now already.