Ok what is the plan? Leaving Kaido to die? Big Mom can still take the poneglyph and still save Kaido who is a literal brother to her.
Why would Lando hand over Han Solo to the Empire? They were like brothers!
Why would Fredo Michaels Corleone brother betray him? They are literal brothers.
Why Mad Eye Moody would be someone else playing him? He literally helped Harry Potter the entire movie!!!
See how this works?