The film wasn't really climactical(it was almost a documentary) in approach. As partial testament to this fact is that I'd probably have enjoyed it just as much watching the sequence of events in reverse. It also could have been chopped up and gone backwards and forwards in time without losing too much. Sure it had a sense of natural progression but imo this took a back seat to the film's atmospheres, characters, themes, scenes and it's moods that were present in every single moment. These for me were mesmerising and "climaxing" from the very start to the finish. The vast open spaces always as a back-drop to contrast with the focused claustrophobia of the main character portraying the neurotic, aggressive, greedy, destructive and vampiristic cut-throat ego white-man with religion in and out of his pocket capitalist business paradigm that has made the planet what it is today. That's also why Agent Smith from the Matrix and the main character from there Will Be Blood remind me of one another(despite the fact they both talk the same way) because they are both representative of the "System". The system has been successfully used......
But to agree to a small degree with what you said, I'd maybe have considered ending it differently.
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From the point where he is in his grand mansion onwards, the film got a little bit weaker for me. It was still good. But ending this movie would have been a little bit tricky or awkward because we are still living this present situation in modern life. That's another reason why the movie had no seeming resolution. We are still in this movie. I'd be curious to know if the director had any other considerations that perhaps bucked linearity and tradition. This may have made it too abstract for some. In some regard what he achieved is a credit to the producer as he still made it accessible to the mainstream allowing it to receive awards and acclaim. He still got his message and artistic vision across without having it sink into obscurity or be received with disdain.
Anyhow, I haven't seen it for awhile now and my opinion of movies often changes so my above views are by no means set in stone.
Jon =)