We can appreciate fully this would appear to come from an ESC issue on the surface. Typically these types of damage situations come from the servo having a problem, Or a basic wiring issue to that harness or the RX wires as they are all connected.
The ESC can't actually 'short' those wires from inside itself, and is generally supporting the external short/damage to the point the wires fail as you've seen here. Even a servo not being setup correctly (end point/travel/binding) can lead to these types of problems fairly rapidly.
This is being brought up, so that your replacement, does not have the same issue. Most common topic is the servo EPA not being setup right for the vehicle and the servo overdrives the steering parts of the vehicle. This is sort of like "hard stalling" the servo, and causes a pretty big load.
Wires getting pinched or damage, is the next thing to of course look out for as small damage to the wires can lead directly to a short.