why do electric engines have huge torque at low revs.?

The don't have "huge" torque, they have maximum torque at zero RPM, because they are electromagnetic and the energy is applied externally, from a battery. Full energy can be applied with the motor not turning. Internal combustion engines have many more parts, and rely on the engine turning at a certain speed before they can even run. Since their power increases as speed increases, they have to run at a higher speed to achieve more power, it's inherent in the design. Also there are many other issues relating to inertia and friction because of how they work. A steam engine is NOT an internal combustion engine, it is an EXTERNAL combustion engine. The heat energy is produced outside the engine and introduced to make it work. Since that energy is immediately available at maximum effort, it also has maximum torque at zero RPM.

zxc090

electric engines have the same power throughout the rpm and do not have to build up power like a normal engine. if they lose power it is due to heat and friction of the motor.

internal combustion engines are not as uniform like electric engines and have to deal with more outside influences (air, fuel, spark) which is why they are hard to make uniform power throughout the power band. they also are far more complex and more mechanical. a steam engine is just another internal combustion engine.