Nevermind. I'll explain what I know:
Theory 1:
He died in a ballooning accident and then Rotondo kept his ghost alive by logging in as him.
Theory 2:
Mocheeze never existed. It was all a joke by Rotondo. All those photos of him in the early days are all fake. He never was. People got suspicious so Rotondo just made that story up to kill him off.
Theory 3:
He just left all together