Closing the lid doesn't stop the computer from operating

I close the lid while YouTube is playing and it sounds as if the computer has been stopped. I mean, I no longer hear the YouTube video. I open the laptop 6 hours later and the battery is drained and the history has shown it's been autoplaying YouTube videos. Now I thought these machines were supposed to be intelligent. This does not seem like intelligent behavior, to run my battery down and keep running YouTube while the lid is shut. How is this supposed to benefit me? I can't find in the settings to stop this nonsense behavior of my laptop. Is the laptop really not intelligent enough to see that it's not hooked up to any bluetooth devices and thus there is no reason to keep it running while it is shut?