Ghosts.

It can't just fall down for no reason. Check everything: The hinges, screws in the wall, etc... Find out why it fell down, or it will do it again.

Try to figure out why the TV fell down. It could be anything from a low intensity earthquake (that will be in your local news) to a pet or poor TV mounting and road vibrations… I have been in a few low intensity earthquakes. Flat panel TV’s especially larger ones are susceptible to if not secured. I remember living in San Diego and grabbing the TV to steady it. Even places you don’t normally think of as being earthquake prone can have earthquakes - but that will generally make it to your local news… Unless badly mounted, generally wall mounted TV’s don’t fall down. On the other hand, larger flat panel TV’s are relatively easily knocked over if not secured.

Gravity? That is, if you're one of those sheeple who "believes in" gravity. It's just a theory!

Maybe the duct tape around it became loose. Add another layer.