>Why does existence exist?
Because, if we were to posit that existence DOESN’T exist, it would contradict its own definition.
If you want to be this skeptical about existence itself, then you should really rethink your life. Skepticism wasn’t mean to be applied in this way, hence why I really have a distaste for these modern “skeptics” who won’t believe in anything unless it fulfills their ever changing criteria for “evidence”, even though that criteria is subjective according to their own biases, not even making it skeptical in the first place.
Don’t be like them, ask reasonable questions, don’t just ask nonsense on /sci/ accompanied with an anime picture.