No killer was sent, but the one threatening the Baratie has always been Germa only.
So Big Mom, while chasing Luffy and Sanji, while having the Germa wrecking havoc on WKI, while BB pirates stormed her kingdom, should have followed a plotline that didn't involve her. Makes sense.
Meanwhile, all her commanders are defeated or dead, and her whole kingdom has collapsed, probably.
One Piece stopped making sense when if you are dehidrated you don't die, and if water touches you you are back to normal, or when Bir D Cage happened, or when a deadly poison doesn't kill anyone.
We all know you have a bias against a Sanji centric arc, but at least hide it.