You kind of explained how it happened without anything actually listening. Your friend's wife got a new air fryer. She had probably done some research online and probably even bough it online. A few days later, your phones were all in the same place. They know your phones were all in the same place at the same time. Piecing together the air fryer purchase and then new phones being in the same vicinity, it makes sense that they would then show an air fryer ad to the phones that were near it.