I’m not a big fan of Alien, in part because its cobbled-together seams still show. They were clearly screwing around with various notions. A lot got discarded, and some only seem partuially discarded. If you followed the fan magazines before its release you saw a lot of the tried-out-and-discarded stuff. (Especially interesting to me was the pre-H.R. Giger artwork. I think Giger made that movie. If he hadn’t come on board, I don’t think it would have been the success it was.) They tried out the idea of the Alien creatures being “worshipped” by the inhabitants of the planet, with a big rock “tomb” filled with carvings and hieroglyphics of the creature’s life ctycle. Obviously, no crashed alien ship in that version. They replaced this with a version with a crashed alien ship belonging to other aliens that they investigate, but lost the evocative tomb and hierglyphic stuff (although I notice they got to recycle this in the recent Alien vs. Predator flick). They tried a version in which the computer “Mother” sides with the alien, because it’s a more perfect creature. They tried doing the same thing with Ash as a robot instead of Mother. They probably tried a version in which the Corporation sent them there on purpose.
Foster’s details in the novelization certainly aren’t gospel (his explanation of how Palpatine became Emperor in Star Wars – everybody’s convinced he wrote the novel, not Lucas – doesn’t fit the storyline of even the second movie). Later Alien movies certainly felt free to muck around with the background.
My sense, when I first saw the film, was that the ship had been diverted there by the emergency beacon and encountered the Alien eggs purely by accident. but Weyland-Yutani, ever with foresight, had started placing androids/robots on board their ships programmed to take advantage of flukes like this to get new resources for the company, even at the cost of other crew members (Asimov would’ve been shocked). That seems like a huge liability and an extraordinary amount of power to put into the hands of an unsupervised android, but , as I say, don’t think the flick was really well thought-out. Besides, without Ash’s interference, the film is over when they don’t let John Hurt’s character back inside because of their quarantine rukles, and the film becomes an interesting short on the hazards of interstellar parasites.