Are you serious?? I'm gonna go head and assume you're serious I guess.
People do not think you can literally see things behind your eyelids. It has jack stuff to do with your eyes.
For most people, closing their eyes tells their brain to not look for visual stimuli—because their eyes are shut. It also removes visual distractions. This leaves room for the brain to focus and think without having to process visual information.
Don't be so loving asinine about something you've given little thought to. "Lmao wtf is wrong with people tryna tell me I can see my mind with my eyes closed loving BS"