The director told a story where Jeremy Lion's Iron's passport wasn't good and he couldn't get to the US to film. And it was like Memorial Day weekend so trying to fast track through the bureaucracy was even more impossible. Somehow they pulled it off at the last second and got him there.

I imagine something like that on your first movie would take years off your life. It's a super important character so you really need an actor of stature, not just throwing a suit on the 1st AD.