If you are like me then you played the Resident Evil games back when they were very much secluded, atmosphere-driven survival horror games. And you might have been puzzled by the departure of the movies from the official lore of the games.
Director Paul W.S. Anderson gives his explanation for that in the video above, where he basically says that a wider audience are probably not going to want or be able to digest the narrative of the series as found in the original games.
One thing that can be said is that although Anderson abruptly replaced George Romero as director in the first movie, Romero’s script wasn’t an exact replica of the old game either. From what I can remember, reading it 15+ years ago, it was the first thing I noticed.
However Romero promised that the theme would be faithful, I’m guessing that was probably true and the reason behind his dismissal.