Honestly, I don't really know why Mr. Stark does anything. From the way he acted around me later, I think he figured out it was a terrible idea afterwards? And I don't think he really thought it would get as insane as it ended up being? I mean, the Ant-Man turning into Giant-Man thing came completely out of left field. And that was sort of the tip of he iceberg when it came to how much of a mess it turned into.