Database

[{aggDate:"2019-05-23",results:[{foo:0.58,bar:0.42},{foho:0.32,bar:0.98,sdbar:0.98,}]}]

Query

db.collection.aggregate([{"$project":{"aggDate":1,"result":{"$let":{"vars":{red:{"$reduce":{"input":{"$map":{"input":"$results","in":{"$objectToArray":"$$this"}}},"initialValue":[],"in":{"$concatArrays":["$$value","$$this"]}}}},"in":{"$arrayToObject":{"$map":{"input":{"$setUnion":["$$red.k"]},"as":"m","in":{"$let":{"vars":{"fil":{"$filter":{"input":"$$red","as":"d","cond":{"$eq":["$$d.k","$$m"]}}}},"in":{"k":"$$m","v":{"$divide":[{"$sum":"$$fil.v"},{"$size":"$$fil"}]}}}}}}}}}}}])

Result