VIewControllers are not getting de-initializing on switch

I believe changeMainViewController expectation is to remove all view controllers from the memory and load new view controller but as per my testing none of the view controller are de-initializing.

Reproduce -
1. Open Sample project
2. Add deinit code in SwiftViewController ```deinit { print("Swift Gone") }```
3. Add deinit code in JavaViewController ```deinit { print("Java Gone") }```
4. Now switch to menu's neither deinit will be called nor viewDidLoad will be called.

Start in the sample project and trace changeMainViewController while switching between SwiftViewController and JavaViewController. Reproduce the issue with the reported deinit and viewDidLoad logging, then inspect why the old controllers remain alive. Done means switching menus deinitializes the previous controller and loads the new controller as expected.

Written by the indexing model from the issue text.