That would require very good mixing of the fuel and oxidizer before explosion, which is unlikely to happen during a launch failure. IIRC for the N1 falling back

That would require very good mixing of the fuel and oxidizer before explosion, which is unlikely to happen during a launch failure. IIRC for the N1 falling back on the pad after a few seconds of flight it is estimated that only a fraction of the fuel load was exploded and unburnt kerosene was raining for many minutes.