Because we're not in heaven..? I'm not sure if it's logical to wonder why he created evil. Because we have opposites of everything, it's one of the scientific, universal laws. And that's how good and evil was created too. So, since God is the creator of everything, he's also the creator of universal laws. Of course that's how 'Satan' is now everywhere. I'm guessing that according to religion, earth where we are now is just "in the middle" meaning we have both, and the purpose of religion is to either get to the negative opposite (hell) or the positive opposite (heaven). Sorry for my lame English, I'm sure I didn't make much sense there.
I'm not sure if I understand your point with that video lol