I didn't say Sabo knocked out the admirals at all, that would be crazy, Sabo isn't the World's Strongest Man or some shit
but there was a fight at least, as we can see by Fujitora's bandages, they at least clashed
and they still got away with it, while also bringing Kuma with them
that was a nice feat
in my mind it makes no sense that two Admirals couldn't stop them, but that's what Oda wanted, so nothing we could do about it