WPF MVVM: Binding a different ViewModel to each TabItem?

Question

I have a main window with a tab control containing 2 tabItems:

I currently

Answer 1

No sure why the selected answer is suggesting to use ObservableCollection and create a collection of tabs and then reference them by index.

I find it more clean to do it this way:

MainViewModel tab1= ConfigViewModel Tab2 = UserProfileViewModel

in MainViewModel:

private ConfigViewModels _configVM;
public ConfigViewModels ConfigVM { get { return _configVM; } }

private UserProfileViewModel _userProfileVM;
public UserProfileViewModel UserProfileVM { get { return _userProfileVM; } }

public MainViewModel(){

_configVM = new ConfigViewModels();
_userProfileVM = new UserProfileViewModel ();
}

In th XAML file:

I'm not sure I understand the benefit of doing this through an observable collection.