The other aspect is that the electrical parts of the power system are lighter at the higher frequency too. A 400hz transformer is meaningfully smaller and light

The other aspect is that the electrical parts of the power system are lighter at the higher frequency too. A 400hz transformer is meaningfully smaller and lighter than a 50hz one. This is the same idea as switching power supplies but planes had to solve that before power semiconductors were cheap enough. The power frequency also has an impact on the size of all the induction motors. I guess if you were designing it from scratch today you would let the generator produce power at whatever frequency the mechanical engineers tell you they want to and the power electronics could convert it without problems. You would do the same thing the other way around on the motors.