for the follow query :
select count(*)
from MEGA_CONTACT
where CivSelection = 2

I have this result in mongoshell

db.getCollection("MEGACONTACT").aggregate(
[
{
"$match" : {
"CivSelection" : NumberLong(2)
}
},
{
"$group" : {
"id" : {

            }, 
            "COUNT(*)" : {
                "$sum" : NumberInt(1)
            }
        }
    }, 
    { 
        "$project" : {
            "_id" : NumberInt(0), 
            "COUNT(*)" : "$COUNT(*)"
        }
    }, 
    { 
        "$project" : {
            "_id" : NumberInt(0), 
            "COUNT(*)" : "$COUNT(*)"
        }
    }
]

);

the second project is not utile no ?