Historiography achieved this aim in two ways: in the process of accumulating data, it provides minimal inclusion requirements for all proposed narratives. The path may wind in a number of ways but ihas to traverse these loci. Having to include these in their belly makes simplistic stories pop like an over inflated balloon or complex stories hang themselves in their own skein.
Furthermore, in re-emplotting new stories, it breaks facile binary disjunctions. The nice thing about binary disjunctions is the hard either-or which can prove the one by the proof of the negation if the other. Re-emplotments add terms to the disjuncts, other ways the stories might have gone, requiring proof by cases to settle the matter.
The fundamental problem of historiography is that historical knowledge is non-monotonic. Any new factoid could change everything. The best bet for the science then is to have a small number of maximally distinct narratives.
The process of factoid generation and re-emplotment serves to maintain the set as small yet distinct.