Further, he uses the statistic that there may be 5X as many Uber on the road as taxis. That's not a problem! That's a solution. Taxis were clearly not addressing the full transportation need, not nearly! Only 20% of potential customers were being served.
Public transit can work for predictable, regular trips. But most busses I've ever been on have been nearly empty. The theatre of supporting public transit (busses anyway) is expensive too.
To replace cars significantly, busses would have to run on most main streets in a regular grid pattern over the entire city over the entire day. Nobody does that. Instead they run irregularly over favored routes (hotspot to hotspot). Which gains some riders at some times of the day.
I'm not sure busses are even an ecological gain in most cases.
Public transit isn't a solution: it's slow, filthy, relatively expensive (for the value received) and public (I'd rather not sit next to someone who hasn't bathed this week). Uber, OTOH, is fast, clean, cheap-for-the-value & private.
Am I really stoked on Uber-the-company? Not really. But I love Uber-the-service. It's far better than taxis and buses.