He'd been taken over by Loki - the younger adopted brother of his protégés boyfriend. He, a serious scientist, had been mind wiped by a God from a recently discovered realm, which calmly blew all current scientific theories out of the water.
He had quite a lot of fun laughing in their faces - it was kind of payback.
Now he knew he would never be able to show his face - he'd been taken over by an insane megalomaniac and tried to help him take over the world.
He couldn't believe it - even though he'd taken control of him, he couldn't believe he was capable.
Perhaps he wasn't. That was why he'd built in the safe gate to shut off the tesseract.