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.

One Piece: Every definitive death in order - Dexerto

Would Zoro Betray Luffy?

Luffy Has Only One Loyal Straw Hat Crew Member Who Would Never Betray Him, Everytime Luffy Was Stabbed in the Back in 'One Piece

One Piece' Preview Sees Sanji Betray Luffy

One Piece Chapter 1034 - Why Sanji's fight is important

One Piece' Preview Sees Sanji Betray Luffy

Did Sanji and Nami ever leave the straw hat crew? - Quora

Why didn't Sanji go easy with Luffy during their 'fight'? - Quora

Spoiler - One Piece Chapter 1078 Spoilers Discussion, Page 515