One analysis I heard is that the vote fraud is a distraction/smokescreen for the real aim: have large swaths of ballots thrown out that could give Trump a technical victory (such as where poll observers were kept too far away from vote counting). If not this, to tie up states in litigation so that they do not certify results in time and republican state legislators send Trump electors, and finally, tie up enough states so that neither candidate receives 270 EC votes and causing a contingent election, where Republican advantage in small states would allow them to elect Trump.
I find all these scenarios to be quite unlikely, but if they were successful, it would indeed be the darkest timeline. You'd have two presidents who claim legitimacy, and recognized by a mix of foreign leaders. There would be blood in the streets. The fact that so many Republicans are playing along with this is pretty disturbing.