Did Banu Ummaiya Start Eid Sermon Before Salah
It has to do with Eid Sermon, not Juma Sermon. It was Marwan who initiated (the practice) of delivering khutbah (address) before the prayer on the ‘Id day to make people listen to him. Because of his poor ratings, he feared that if he delivered Sermon after Eid Salah, then people would not sit around to listen to him, which according to him was humiliation. So in order to avoid that humiliation, he started this practice. https://sunnah.com/muslim:49a