Battery voltage is going to be drawn down during cranking due to the high current demand of the starter motor. Since we start with a lower voltage at the ignition switch, there is going to be even less at the coil, . . . possibly enough less that it won't develop sufficient voltage to fire the spark plugs. Bypassing the resistor during cranking will put that lower battery voltage at the coil so it will be operating at its design voltage again.It gets the bypassed full battery voltage from the IGN 2 circuit of the switch .