Am I the only one who believes that the overload is merely coincidence and has nothing to do with whether or not the motor decided to take a dump that day and cause the fire?

Overloaded circuits should trip breakers and overheat wires, but each device on the circuit should operate normally. The only exception I can think of is if the motor was trying to draw 25A and perhaps it only had 16 ga wire to it or something. Although even in that case, the wire, not the motor, would be vulnerable.

How about its just an old motor that decided to fail in a horrible way that day?