In Dark Sector's case, I'm sure the devs saw that 360 gamers really just wanted to shoot the hell out of stuff, and knew that the typical 360 gamer just loves blood, guts and violence especially since GeoW made huge splashes before it's release and ended up being the best selling 360 game ever made until it was beaten by Halo 3 IIRC (blood guts and mayhem in, stealthiness, Snakey-ness, Sam Fishery OUT).
Dark Sector's initial concept was very interesting, but perhaps the whole stealth genre had been too overcrowded by that point, but I do hold a firm grip in my believe that the devs of Dark Sector truly sold themselves out, but many devs do because of course, they want to make money. I was sorely dissapointed when Dark Sector came back into the limelight only to be a GeoW clone. I still like watching the original concept video, such a good mixture of nice lighting and shadowing (very 2004-2005 look to it but still very nice), stealth, mechanical design, and some of the combat (like when the main character is fighting that large robot). Oh and how could I forget the great score using Taiko drums? That was arguably what sold it over to me concept wise, it's just to bad that it didn't turn out that way
But yeah, developers have to make money, and by following someone else's lead they can hope to emulate the same success hoping fans of one game can cross over and feel right at home in theirs. Halo for instance influenced many Xbox games to have similar control schemes and of course Halo is considered the catalyst for the "2 Weapons + grenades" outloading, though the Rainbow Six games had been doing a realistic load out years prior (main weapon + sidearm) but being a realistic game it was supposed to I guess you could say.
Also during development time, tastes in the consumer change (Dark Sector I think is a good example of this) and the devs can only react so quickly. Then you have to take into account critical and gamer reaction, especially with violent games that could end up screwing the developer and publisher out of profits like in Manhunt 2's case since it was banned in the UK until the game had been revised.
This could go on for hours........so I'm gonna stop. But one more thing that I've always wanted to know: Why the HELL was Ace Combat 3's NA and EU localization so cut up and torn apart from the original Japanese version?!?!?!?