Пустой Combobox WPF

Проблема в том, что когда делаю binding данных в XAML, то комбобоксы пустые, если же передать их в конструктор создаваемого окна и там напрямую сделать ItemSource = коллекция, то ситуация противоположная. Коллекции загружаются до создания окна и поэтому не могут быть пустыми, но почему тогда происходит такая ситуация?

    internal class ProductForSaleViewModel : ViewModel
{
    private readonly IProductForSaleService _service;
    private readonly IProductService _productService;
    private readonly IStoreService _storeService;
    private readonly IProductDeliveryService _productDeliveryService;
    private readonly IPackagingService _packagingService;
    
    private ObservableCollection<ProductForSale> _productForSales;
    
    private ObservableCollection<Product> _products;
    private ObservableCollection<Store> _stores;
    private ObservableCollection<ProductDelivery> _productDeliveries;
    private ObservableCollection<Packaging> _packagings;
    
    #region Команды

    #region  GetCommand

    public ICommand GetCommand { get; }
    private bool CanGetCommandExecute(object p) => true;
    public async void OnGetCommandExecuted(object p)
    {
        ProductForSales = new ObservableCollection<ProductForSale>(await _service.Get());
    }

    #endregion

    public ICommand AddEditCommand { get; }
    private bool CanAddEditCommandExecute(object p) => true;
    public async void OnAddEditCommandExecuted(object p)
    {
        await LoadComboBoxes();
        var page = new AddEditProductForSalePage();
        page.Show();
    }
    #endregion

    public ObservableCollection<ProductForSale> ProductForSales
    {
        get => _productForSales;
        set => Set(ref _productForSales, value);
    }

    public ObservableCollection<Product> Products
    {
        get => _products;
        set => Set(ref _products, value);
    }
    public ObservableCollection<Store> Stores
    {
        get => _stores;
        set => Set(ref _stores, value);
    }
    public ObservableCollection<ProductDelivery> ProductDeliveries
    {
        get => _productDeliveries;
        set => Set(ref _productDeliveries, value);
    }
    public ObservableCollection<Packaging> Packagings
    {
        get => _packagings;
        set => Set(ref _packagings, value);
    }

    public ProductForSaleViewModel(IProductForSaleService service,
        IProductService productService,
        IStoreService storeService,
        IProductDeliveryService productDeliveryService,
        IPackagingService packagingService)
    {
        _service = service;
        _productService = productService;
        _storeService = storeService;
        _productDeliveryService = productDeliveryService;
        _packagingService = packagingService;
        
        GetCommand = new LambdaCommand(OnGetCommandExecuted);
        AddEditCommand = new LambdaCommand(OnAddEditCommandExecuted);
        
        _productForSales = new ObservableCollection<ProductForSale>();
        OnGetCommandExecuted(null);
        
    }

    private async Task LoadComboBoxes()
    { 
        await GetProduct();
        await GetStores();
        await GetProductDeliveries();
        await GetPackagings();
    }
    
    private async Task GetProduct()
    {
        Products = new ObservableCollection<Product>(await _productService.Get());
    }
    
    private async Task GetStores()
    {
        Stores = new ObservableCollection<Store>(await _storeService.Get());
    }
    
    private async Task GetProductDeliveries()
    {
        ProductDeliveries = new ObservableCollection<ProductDelivery>(await _productDeliveryService.Get());
    }
    
    private async Task GetPackagings()
    {
        Packagings = new ObservableCollection<Packaging>(await _packagingService.Get());
    }
}

Представление:

<Window x:Class="CandyKeeper.Presentation.Views.AddEditPages.AddEditProductForSalePage"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:local="clr-namespace:CandyKeeper.Presentation.Views.AddEditPages"
  xmlns:iconPacks="http://metro.mahapps.com/winfx/xaml/iconpacks"
  WindowStartupLocation="CenterScreen"
  WindowStyle="None"
  AllowsTransparency="True" Background="Transparent"
  DataContext="{Binding ProductForSaleViewModel,Source={StaticResource Locator}}"
  Title="AddEditProductForSalePage" Height="400" Width="300">
<Border Background="#dbdae0" CornerRadius="20"
        MouseDown="Border_MouseDown" MouseLeftButtonDown="Border_MouseLeftButtonDown">
    <Grid>
        <StackPanel
            VerticalAlignment="Center">
        
            <Button Style="{StaticResource gridRemoveButton}" Click="CloseBtn" Width="25" Height="25" Margin="250 0  0 0">
                <iconPacks:PackIconMaterial Kind="Close" Style="{StaticResource gridButtonIcon}"/>
            </Button>
            
            <TextBlock Text="Кондитерские изделия" Grid.Row="1" FontSize="14" FontWeight="SemiBold" Margin="0 10 0 0"
                       HorizontalAlignment="Center" Foreground="#121518"/>
            
            <!-- Заполнение данных-->
            <TextBlock Text="Продукт" Margin="50 20 0 0"></TextBlock>
            <ComboBox Width="200" Name="ProductComboBox" ItemsSource="{Binding Products }" DisplayMemberPath="Name" SelectedValuePath="Id"></ComboBox>
            <TextBlock Text="Магазин" Margin="50 0 0 0" ></TextBlock>
            <ComboBox Width="200" ItemsSource="{Binding Stores}" DisplayMemberPath="Name" SelectedValuePath="Id"></ComboBox>
            <TextBlock Text="Поставка" Margin="50 0 0 0"></TextBlock>
            <ComboBox Width="200" ItemsSource="{Binding  ProductDeliveries}" SelectedValuePath="Id"></ComboBox>
            <TextBlock Text="Расфасовка" Margin="50 0 0 0"></TextBlock>
            <ComboBox Width="200" ItemsSource="{Binding Packagings}" DisplayMemberPath="Name" SelectedValuePath="Id"></ComboBox>
            <TextBlock Text="Цена" Margin="50 0 0 0"></TextBlock>
            <TextBox Width="200"></TextBox>
            <TextBlock Text="Объём" Margin="50 0 0 0"></TextBlock>
            <TextBox Width="200"></TextBox>
        
            <!--Сохранение-->
            <Button Style="{StaticResource addButton}" Height="30" Width="100" Margin="100,40,100,0">
                <StackPanel Orientation="Horizontal">
                    <iconPacks:PackIconMaterial Kind="ContentSave" VerticalAlignment="Center" Width="11" Height="11" Margin="0 1 8 0"/>
                    <TextBlock Text="Сохранить"/>
                </StackPanel>
            </Button>
        </StackPanel>
    </Grid>
</Border>