Why every time the elements on the page are cleared xaml?

Question

C++ / C#

I keep all the ViewModels in the IOC, and I reload the pages and leaving the pages on return, a new instance is naturally created and everything is empty there, at first I thought that maybe I also need to keep the pages in the container, but then I noticed that, for example, the ListView remains on the page. despite reloading the page, is it made as a singleton?
The question is where is the problem, in my custom elements and controls, that they are not singletons, or that the page is reloaded every time?