Proof of concept! With buses it would be easier to change/add routes, and the infrastructure might be cheaper.

I had a professor in one of my environmental science classes back in college who was from California. He didn’t drive an EV, and received a lot of flak from his colleagues because of it. He would always explain to them that the majority of the electricity in his area came from coal, and driving an EV wouldn’t be any better for the environment than a small gasoline powered car (what he drove) if you just counted emissions… but if you count the landfill space and the mining of the lithium for the battery of the EV (they hadn’t developed great ways to recycle the lithium by then either) the small gas vehicle kept for 15 years or so would be far better.

He was one of the few I encountered in that field with any sense at all.