Marco also sent Aokiji flying when latter was trying to kill Luffy. Akainu didn't notice an old dying Whitebeard appearing behind him. You don't always have CoO active. So if those admirals didn't have CoO active all the time during war, why should Kaido during a feast.
Also, Kaido can allow himself to be more reckless, since he is durable enough to tank most stuff anyways.
Also, Kaido can allow himself to be more reckless, since he is durable enough to tank most stuff anyways.