If I were to guess I'd have to say that there was probably a short somewhere in windings on the motor.

And as far as it being cooked, it could just be the cap, it could be the whole ESC.

First thing I'd try is running a different motor, doesn't matter the wind as long as it's within the limit, on that ESC. Replace the cap with a new one and wire up as per usual. If that's not the ticket then next I would test the motor with a voltmeter to check the wires.

If one reads funny, the motor cooked the ESC, and it will probably continue to do so on every unit you use it with. If it reads fine, might have just been a short elsewhere, make sure when you re wire it all that everything is by itself, nothing visibly touching.