for some reason Firebase is returning promise instead of value

let customer123 = db.collection('CustomerDatabase').get().then((snapshot) => {
    snapshot.forEach((doc) => {
        if(businessNameValue === doc.data().BusinessName){
            let customerID = doc.data().CustomerID;
            console.log(customerID) // this is fine, i am able to ge the value.
            return customerID
        }
    })
})

console.log(customer123) //but this is giving me promise