He changed. he wasn't the same Sanji you knew before, his usual sweet, dorky and silly personality is replaced with cold and sinister vibe. he changed because of his 'family'. He thought you'd love this side of him - it's a side of him that's more stronger than the old Sanji but it was the opposite. you couldn't believe he changed himself, you didn't like it. you missed the old Sanji, you need him back.