Well there's the phases (pairs of magnets opposite to each other in the squirrel cage and opposite in polarity to create field lines) in the AC Motor and they're all electromagnets.
And these phases (pairs of magnets) change, there's changing the magnetic flux. Now the rotor has an induced current and as Lenz's Law states the induced EMF/Current will oppose the change in magnetic flux that created it.
Therefore the eddy currents in the motor will oppose in magnetic flux that created the currents.
This causes the rotor to spin.
(in simple language, it doesn't like that change in magnetic pairs. therefore the rotor tries to return back to its normal. But since the magnetic pairs are always changing the rotor is always trying to return back there spinnning).
Hope it helps.