Why AC induction motor is used for high power applications?
DC motors require commutators. All of the mechanical output power must be transferred to the rotor through the commutator. The maximum voltage and current for which a commutator can be designed limits the maximum power for which DC motors can be designed. AC motors don't have that limitation, so they are used at power levels that DC motors are either impossible to design or very difficult to build.

Even at power levels for which DC motors have commonly been used in the past, the commutator poses a maintenance and reliability problem. As economically competitive variable frequency induction motor drives have matched and exceeded the performance and reliability of DC motors and controllers, they have become the preferred alternative for most uses.

Above some power level, wound-rotor synchronous motors are used rather than induction motors. That may have to do with some design issue, efficiency, manufacturing cost or some combination of factors.

Product line descriptions of various manufacturers indicate that induction motors are available with ratings up to at least 10,000 horsepower (7.5 MW). Wound-rotor synchronous motors are available with ratings up to 135,000 Hp (100 MW). Synchronous generators are available with ratings up to at least 2000 MW. Synchronous generators have been operated up to 380 MW as motors in a pumped storage hydroelectric plant.