So far i saw now, Kid left cause beside Apoo there came some others People, like Queen or the Numbers. Wait for the chapter for evaluate. But Apoo got hit Pretty hard from the pic i saw. Seemed to be extremely painfull.
Kaido is allied with the second strongest nation in the world yet his crew was never shown to be ahead of other emperors, on the other hand Big Mom was fully confident that she could destroy all emperors if she was allied with Elbaf. And it's not like she doesn't know how strong they are, she fought Roger and Garp in the past and the other emperors are around that level as well.