I’m not sure Hulu supports the ability to navigate away from the tab and continue watching. What you’re doing in Hulu is using the “mini player” which makes the window small so that you can continue browsing in Hulu. But if you navigate away from the tab, the video disappears as well.
For example, I’m testing this in Firefox on my end and I see the same behavior in Brave:
So this is reflective of the player Hulu is using, not the browser it’s being used in. If you navigate away from the tab playing the video in Firefox on your end, you should see the same thing.