Long cables to ESC could be reason for fire, but I do not see any relation between long cable and fire in the case of crash (loaded or stopped motor).
The battery is a peak filtering component in the ESC circuit. Its task is not to allow the motor inductance make high voltage peak when FET transistors switch off the feeding of motor coil. Disconnected coil makes back current which should go back to battery and the battery must "accept" that current. If the battery is not present, or if that battery is separated by long wire with some self inductance, than FETs must survive high voltage peak, and it can damage them .... the result is fire. The same happens when you disconnect arming plug during motor run.
So the solution for arming plug is:
1/ do not disconnect arming plug during run. (well … sometimes it less harmful to save life than risk ESC :- ))) )
2/ if your leads are visibly longer than usual (typically 10”) add LOW ESR capacitors somewhere in the middle of the cable. Good advice is to use the same capacitors as you see on ESC. (the same type, the same voltage and the same size)
3/ you will probably see that connecting battery makes larger spark then before (because of twice higher capacity). Solution is anti spark resistors. Unfortunately some ESC makers does not allow anti spark resistors because they do not add ESC switches (like CC) and slow voltage rising can “confuse” processor, so it is better either to use ESC with switch, or to install switch to the timer, so the timer does not sent arming signal during connecting battery. Use that switch also in case that you want stop motor … it is there for that purpose.