Because of the massive undertaking that the trilogy was, it was going to require a serious commitment for everybody involved.
Mission: Impossible II’s Dougray Scott says that he was sent a copy of the script, with the possibility of him playing the role of Aragorn.
He explains that, while he thought the movies looked great, he ultimately couldn’t reconcile the idea of spending two years in New Zealand making them.
And it was that commitment which apparently turned off at least one potential actor.