[{"date":"15-12-2020","name":"alice","money":7},{"date":"15-12-2020","name":"bob","money":9},{"date":"16-12-2020","name":"alice","money":39},{"date":"16-12-2020","name":"bob","money":25}]

db.collection.aggregate([{"$sort":{"money":-1}},{"$group":{"_id":"$date","max_money":{"$max":"$money"},"the_person_with_max_money":{"$first":"$name"}}}])