How does propulsion of diesel and electric (trolley) buses differ?

Less weight. And, electric motor has more torque.

Right. The reason why regular trains are diesel powered electric is because with electricity driving the wheels you have 100% torque instantly. With a regular diesel piston engine you would need a clutch the size of a Ford truck, and it would wear out often.

Torque of an electric motor is 100% at start, but decreases with RPM. Diesel (and gasoline) engines need to get up to speed before they have usable torque.

Diesel electric trains run up the diesel engine to an efficient RPM to power a generator. The electrical power goes to electric motors. This is perfect for getting a long train moving.

If you want an effective demonstration of the difference in power delivery between electric motors and “regular” engines, watch some of these videos

That car has a pretty low HP rating, but has more torque than the V-10 out of a Dodge Viper. The lack of HP and it’s old-school boxiness hurt its top end, but it’s 0–60 time is better than damn near any other street-legal car, including expensive supercars. And that ability to accelerate is just what it takes to haul a heavy load (like a train) or climb a hill.