Oda can't write logical characters.
An arc before we had the supposed mastermind Bigmom who decided randomly to kill off Sanji's family for no reason. She has been getting married into dozens of other families (even boss killer Bege) but for no explained reason, when it came to one of the main cast's family members, she decided to kill all of them during the wedding, in front of every ally she has and even invited the most famous journalist in the world to make sure no one would trust or decide to marry one of his daughters again.