This earlier question about a seemingly trivial change preventing a nuclear war made me remember a short story I read more than 20 years ago.
In the story, there are 2 intelligences (it is not clear if they have any physical form) that are able to randomly access time. They take turns making a few minor changes to human history and observing the results. I think the story starts with them picking which outcome each is playing for, and then one stating that it will go first.
The first makes a few changes (details forgotten), and they observe that the result is Earth becomes a nuclear wasteland. Then the other takes its turn; as best I recall it makes 3 changes. The one I remember most clearly is that it kills Cato the Elder (by some medical condition like a stroke or aneurysm) before yet another "Carthago delenda est". (The implication being that the 3rd Punic war is averted.) The other 2 changes were similarly minimal, but I have only an impression that they may have involved other historical figures.
Fast-forwarding, the intelligences find a thriving space-going civilization, and the first congratulates the second, remarking that it had not expected such small changes to have such a large effect.
The story ends with one suggesting to the other "best 2 of 3?"
This may be a conflation with another story, but they may have picked the outcome each was playing for in terms of "blood" (life) and "dust" (death).
I definitely read this more than 20 years ago, but probably less than 30. It was most likely in an anthology, since I didn't have many single-author collections at that point. (But I can't rule that out, or that I might have read it in a magazine like IASFM or Analog.)