The Fat man was sucessful in brain washing Leila. He told her that if she would continue dancing, she'll grow old and will one day be sitting in that crowd of old people who only sat watching the young couples dance. Because of her innocent nature Leila believed every word the fat man told her. He told her that she would have to stop dancing or else she would be amongst those people in the crowd one day. So fat old man was able to brain wash Leila and due to her innocent nature she fell for it.