How to handle WKWebView memory optimisation in app (ios)?

Guys, please help to figure out what is going on.
My app shows some videos for end user. When user switches to other app, and my app staying in background for a while, next time user see white screen and process of reloading videos/images that was in app;

  • Why does ios do not terminate whole app, but terminate only ‘Web’ part of it? (And do it partly: hook ‘OnAppStateChange’ - works;)
  • How to handle that things correctly? Is there any workaround to recognize, that app now reloading stuff due to memory optimisations ?
  • Why splash screen do not shown each time when it happens ?