Tidal locking is what makes the Moon rotate about its own axis at the same rate

Suppose that the masses are oriented so that the rod is along a radial line from the planet. The forces on the two masses are unequal, but they are lined up, so there is no tendency to turn. If the rod is turned a small amount, the mass nearer the planet is attracted with a larger force, so there is a net torque directed so as to orient the satellite the way it was originally. If the rod is turned through 90°, the torques are again in equilibrium, but this is an unstable equilibrium because a small displacement away from that position will produce a torque in the same direction as the rotation of the rod.