Capacitors for EV energy storage have never succeeded, because they just don't work very well. Part of the problem is that while batteries change in voltage by only a small fraction of their nominal voltage with a change in state of charge, fully discharging a capacitor means taking its voltage to zero (obviously not practical), so only part of the potential energy stored is usable.It also depends on super/ultra capacitors. Still in its infancy, but. I do fancy capacitors. Hoping for 70-80 mile range.
There were some hybrid buses with capacitors instead of a battery, but their storage requirement is very short duration compared to a purely electric vehicle, and due to the size of the vehicle the peak power requirement is high.