You're probably imagining an assembly line, where one step follows another in a logical procession, and there doesn't seem to be much of a branching factor. However, each step along that line is the process of many deep optimizations. It is more complicated than you think; thousands of people work on it. Consider just the case of choosing a screw, probably one of the most simple steps in building a car. These 24 pages only scratch the surface of the choices available: http://www.fastecindustrial.com/images/MediaCatFastener.pdf