You could let teslas in bus lanes and they wouldn't be overflowing with traffic, that's hardly the point. Bus lanes should be for vehicles that add very little to congestion, either because of the number of people transported (as in the case of a bus), or because of the size of the vehicle (bikes, motorbikes, e-scooters).

Black cabs (and ubers) have an effective occupancy even lower than private cars.

A lot of cab and uber use in London is groups not just singletons - its cheaper for 3 or 4 people to use a back cab or uber for short journeys than use the tube

So allow high occupancy vehicles (say at least 3 passengers, 4 for taxis) in bus lanes.