Hello kc50karim,
Thanks for getting back to us with those additional details, and this helpful video. It looks like your Magic Keyboard for your iPad backlight is not working as expected, so let's continue working on this together.
Let's test if adjusting the brightness of the keys manually works differently by following these steps:
"Like an iPad, the brightness of the Magic Keyboard automatically adjusts based on the light conditions around you. If you want to manually adjust the brightness of the keys on your Magic Keyboard, go to Settings > General > Keyboard > Hardware Keyboard."
Do you have Dark Mode, Night Shift, or True Tone turned on your iPad's settings?
Adjust the screen brightness and color on iPad
iPadOS 15.0.2 was recently released, so if you haven't already, please back up your iPad, and update:
Back up iPad
Update iPadOS
If your iPad is up-to-date on software, let's try to restart it by following these steps:
Restart your iPad
If the behavior persists or you run into any trouble, please reach out again.
Best Regards.