Either coincidental bad luck or a wire got moved by accident during the installation and shorted out.
It is practically impossible for interference on the ESC signal wire to damage any well-designed ESC, invalid input should be ignored and eventually trigger ESC shutdown if it lasts long enough.
Assuming 'short' wires betwixt ESC and motor no external influence other than overvoltage or short circuit on a wire or motor overcurrent should be able to directly cause them to burn.
Signal and BEC is 5V so main battery +V touching either of those wires will probably kill it (and your receiver/autopilot), and 0V touching a BEC output may reset the ESC. If the motor is running at the time it may burn.
Either way, most ESCs live on the edge of disaster by design as they have minimal heatsinking and expect low duty cycles - intended to run for a few tens of minutes and usually in the draft of the prop.
I think was a short circuit.
Thank you very much!