DD applied ED because she loved the school. She wanted to be around really smart students like herself that shared a passion for academics. Look at the stats, half of all classes are admitted early. If not admitted EA to Yale the chances of an RD admit are diminished as they are now competing in a much larger pool. You’re not going to be able to determine what exactly the admissions office is looking for so the only thing you can look at is the rates of admission which are simply higher for ED.