They are closed after a restart.
The multitasking bar serves 3 purposes and doesn't distinguish between app states. They can be non-running, suspended, or using a background API. Essentially, it's a history of the previous apps you've used. Some of them could be suspended which means in ram but not doing anything CPU-wise and some of them could be using background APIs which means they are running a thread or two and using very little CPU and some Ram to do something in the background.
When you restart, every app that is either using background APIs or is suspended is closed. The bar just isn't cleared. If you think of it like a web browser, you don't necessarily clear your history when you close a web browser so it's there the next time you launch it but none of those sites are open. That's essentially what you're seeing.