He wanted to stop them from meeting, we don't know what that would've entailed, could've just spammed lasers at Big Mom's single ship from afar, I mean King and Marco managed to almost kill them despite being vastly weaker.
Whereas Kaido's statement isn't interpretable, "there is no one in this world who can defeat me" -> fought SaturnMu personally alongside Primebeard and Xebec, two of the strongest characters of all time. To pretend like Kaido has no idea what he's talking about isn't cope, it's delusion and downplay.