The most important parts of an electric motor are two: the rotor is one of them. The rotor which is a coil of enameled copper wire behaves like a permanent magnet https://www.mrosupply.com/popular_products/hose-clamp-size-chart/ and its North and South poles, since the electric currents produce magnetic fields. The torque continues until the coil poles reach the opposite poles of the stator. In this situation the coil has turned 90o and there is no torque whatsoever, because the lever arms are zero, the rotor is in stable equilibrium, force and resulting null torques.
This is the appropriate time to reverse the direction of the current in the coil. Now the poles of the same name are very close together and the force of repulsion is intense. Since the coil already has an angular momentum ‘to the left’, it continues to rotate ‘to the left’, it is the inertia of rotation and the new torque guaranteed by repulsion forces, it contributes to the maintenance and acceleration of the rotation movement. As the opposing poles attract, the coil feels a torque that acts in the direction of turning the coil ‘to the left’. The coil undergoes angular acceleration and continues its spin to the left.