Why Did Ridley Change Course?

Hi Everyone! Wow, so much buzz going on here lately with all the reviews and such- I feel kind of stunned. If anything, it just exemplifies how impactful the original ALIEN was; some things just can't be topped, and although we knew there would be disappointment, some folks are really walking out of theaters in a rather nasty mood. But all this makes me think- Ridley seemed very confident in the direction he was taking this film during the early days. He can certainly tell a good story; I mean, he fought to keep in the Space Jockey and that made all the difference in that film (indeed, Prometheus depends on it). I wonder what made him change his mind- what was his original idea, and what about it didn't he like? Even something "simpler"- like exploring the SJ's homeworld in the midst of some interplanetary war- could have been equally (if not more) compelling. Certainly, the films after ALIENS didn't push the storytelling envelope in any way, so it's not like he had to top them. A lot of people would have liked some of the elements we saw in ALIEN kept in and explored in a purer form- no suits, humanoid aliens and grand explorations of deity- it would have been awesome to seen that taken to the next level. I guess I have a lot of Googling to do later, because I'm hoping he explained his motivations somewhere. =)