Originally Posted by Jennifer
Doc's changes led to the end of his life, so the ripple effect hit him quickly. Marty and the DeLorean weren't unaffected by the ripple effect. They were just affected at a slower rate because Marty is still alive in 1986 in the Citizen Brown timeline, and the DeLorean that the time machine was made from still would have been manufactured in the Citizen Brown timeline (as would the base components that made up the gadgets inside of it).
Bullshit. If Doc faded instantly then Marty and the time machine would at least fade in a couple hours.