Trams are surely better, but the simple infrastructure and relative simplicity of the drive train make trolley often cheaper than a diesel bus. Trolley buses with a small battery can also deviate from standard lines or bridge small areas between trolley lines.
When I was there I found those busses really cool. But to my knowledge, they’re being phased out. They essentially combine the worst of bus and tram:
Trams are surely better, but the simple infrastructure and relative simplicity of the drive train make trolley often cheaper than a diesel bus. Trolley buses with a small battery can also deviate from standard lines or bridge small areas between trolley lines.