I have to admit some of the character motivations are plain bizarre. My guess is that the script had undergone so many changes & rewrites that nobody really know who and what anymore. There is a suggestion that Weyland has deeper connection to the Engineer's group. That Shaw & the crew are just experimental subjects not for Weyland but for the Engineers to fiddle with!
Another strange line of dialogue involves David saying" If we don't wear a suit, you people wouldn't be comfortable.." Now there is a lot parallel drawn between David & the Engineers, that they are servants for Higher Authority.That kind of line is too loaded to be thrown around before the most suspenseful part of the movie, the first trip to the temple. The Engineers themselves wear a suit, the elephantine suit, so that they look "agreeable" in the presence of the Higher Authority: the Ganesha/Giant Space Jockey of the original ALIEN.