Or minato could have fought it his mind which only takes 1 sec of real time because minato can beat the kyuubi 1 vs 1But it was said that you can't have two summoings. Minato on the other hand could us KCM because Kurama's Yang and Yin halves both share a mind, so when Naruto's half became cool with him, the Yin half became cool with Minato, allowing him to use it too.