Befe assassination was a theme of the arc. That literally came in the middle of a rescue arc. This arc is taken down the beast pirates. Which is why your seeing SH get more 1 v 1. Just like Wano Oda hinted that only way to stop BM was get her what she wanted food wise. Sanji skills were perfect for the situation. Oda showed at the start of WCI that Luffy not capable of doing this. Let me try to explain how naunce and good story telling actually works.
Beginning of WCI Sanji absent led to low energy SH and Luffy almost dying. Showing Luffy not capable of what Sanji does.
So Oda in the same Chapter made Sanji make his declaration
Oda sets up problem that Sanji can solve using who. A freaking Youkou. He didn't use a underling or commander to give Sanji his moment. He used a Youkou. Alot of people hated BM for the disorder during WCI, but does Oda care. No
She was rampaging people saying can't be stopped without her food. Then Oda even made Struasen a top tier Cook that Sanji will surpass or shown better than by the end of the arc.
Then Oda makes BM anticipate the Wedding and food all throughout WCI and nake Luffy ruin it and the only person who can stop her is who. Sanji at this point. Constantly being brought up. Hunger pangs cant stop her etc...
Sanji makes declaration he stopping BM with Cake and low diff Struasen cooking and BM says best shit she ever tasted in her life basically. Yes he used a Youkou to do this.
The arc ends with Sanji Serving the SH in his role
So when you tell me people constantly bringing up Kaido head getting chopped off and it means noting. Forgive me if i think you can't read and comprehend.
Beginning of Wano Luffy pretending like he a good Swordsman like he pretended he was a good cook
Oda introduces the problem with Kaido
Nobody can take his head
He emphasis over and over again
Yea it didn't matter just like Oda constantly mentioning food and hunger pangs didn't matter for Sanji. Clueless Luffy said himself He can't do cook or cut