There can be many reasons why the original director of a franchise may decide not to return for a sequel, though they all usually have in common that they're very Hollywood-politically-correct. So exactly why Jon Favreau decided not to helm the third instalment of what is, for all intents and purposes, 'his baby' Iron Man, I can't be sure. But I can tell you one thing: something definitely changed.
Everything about IM3 feels different from its predecessors. The atmosphere is darker, which is not to say it's really just a lot less humorous (which is – let's be honest – precisely what we love... read the rest.
Some material may be inappropriate for children under 13. Films given this rating may contain sexual content, brief or partial nudity, some strong language and innuendo, humor, mature themes, political themes, terror and/or intense action violence. However, bloodshed is rarely present. This is the minimum rating at which drug content is present.