it’s also much easier for a city to electrify its bus fleet, vs convincing private citizens to go electric with their personal cars.

I’m curious how/where this data comes from, seems like it would vary a lot, e.g. Seattle and SF have some electric busses using catenary wires, Chicago has diesel-electric hybrids, Bogotá has dedicated lanes so busses aren’t sitting in traffic, etc. Different cities will have different mode share, too, so some systems will have more riders. In Chicago, the train system is distributes inequitably, leading to a higher mode share for the train in wealthy areas and a higher mode share for the bus in poorer areas.