@Petnavis like in Dragon ball? Where trunk go back in time, but his actions created a new timeline. There is two trunks, one that has both parents and the one that has only one parent but was able to learn techniques with goku and went back to his time line to exterminate cell from his time?
or do you really think that the descendant knew that he was going to vanish. I mean yes he would disappear but if we count time and all wouldn't it take sometime until the actual ancestor is able to receive the help of the nanobots? then the descendant would vanish cuz a new version would be form. If that is the case, that is why he probably move to another location because he is targeted and doesn't want the one trying to catch him to know the location of the ancestor he is trying to help to change their family history.