Promise resolved but returns part of data - rest 'undefined'

I'm having an issue with a Promise that gets returned from MongoDB's mLab. Part of the data is passed correctly, rest is undefined. I'm not sure what is going on here.

This is JSON object from a collection in mLab that I connect to.

{
    "_id": {
        "$oid": "591424da932aad14186a7213"
    },
    "name": "Archos Elements 50 Oxygen",
    "weight_oz": 4.59,
    "battery_capacity_mAh": 2300,
    "platform": "Android",
    "date": {
        "$date": "2017-05-11T08:46:18.684Z"
    },
    "dimensions": {
        "width_mm": 70.5,
        "height_mm": 143,
        "depth_mm": 9.9
    },
    "__v": 0
}

This is how I retrieve the data (body-parser is used to capture 'name' of the phone that user inputs via HTML form)

router.post('/page_2', function(req, res){
phone = req.body.phone
mobile_and_tablet_model.find({name:phone}).exec(function(err, result) {
        if (err) 
            throw err;
    }).then(function(MongoDBdata){
        console.log(MongoDBdata[0]) // logs out entire JSON object correctly
        console.log(MongoDBdata[0]._id) // 5002
        console.log(MongoDBdata[0].name) // Archos Elements 50 Oxygen
        console.log(MongoDBdata[0].weight_oz) // undefined
        console.log(MongoDBdata[0].battery_capacity_mAh) // undefined
        console.log(MongoDBdata[0].platform) // Android
        console.log(MongoDBdata[0].date) // 2017-05-11T08:06:27.894Z
        console.log(MongoDBdata[0].dimensions) // undefined
        res.render('page_2.hbs', {
            title: 'some title', 
            phone: phone,
            battery_capacity: MongoDBdata[0].battery_capacity_mAh, // undefined
            platform: MongoDBdata[0].platform // Android
        })
    })
})

Can someone help me understand this behavior & help me fix it ?

I don't understand why am I getting 'undefined' for some nested values on the JSON object. I'm far from being an expert on Promises, but if I understand correctly then promise has been resolved, so the sync/async behavior should not play a role here ? (especially since console.log(MongoDBdata[0]) logged out the JSON content in full).

Much appreciated!

via user7861743