Why did Sanji “betray” Luffy in One Piece?

Whole Cake Island was a very important arc for One Piece fans, since it tested the true companionship between Luffy and Sanji.

List of One Piece characters - Wikipedia

The Inevitable Fight Between Sanji & Zoro (Theory) - Gen. Discussion - Comic Vine

The Forgotten D. and Law's Betrayal - One Piece

Enies Lobby Arc, One Piece Wiki

One Piece' Manga Chapter 846: Luffy And Nami Battle 'Enraged Army,' While Sanji Agrees To Wed Pudding To Save Straw Hats Gang From Big Mom's Wrath

The Betrayal of Zoro

Why Did Sanji Betray Luffy In Anime One Piece? Everything We Know

The 14 Greatest Sanji Fights In 'One Piece,' Ranked

One Piece Made Luffy's Straw Hat Fleet Betray Him (And No One Noticed) - IMDb

Why did Luffy have a fight with Usopp and Sanji? - Quora