Earlier quoted context omitted.
I mean, maybe. Honestly hard for me to imagine war actually going on between two interstellar civilizations. But even if it did, it seems like in 99% of all cases, that would leave at least one of the two civilizations still around. We're looking for explanations, in this hypothesis, that leave 98% of all time with no civilizations.
Maybe war between two spacefaring civilizations is too "easy". eg something like: throwing asteroids at ~the speed of light is necessarily a cheap thing to do once you're at that level, and everyone just dies. Like if on Earth nukes were something everyone could cook up in their backyard in an afternoon, we'd all be gone pretty quick. Not sure that really makes any sense though.
The Killing Star[0] and Flying to Valhalla by Charles Pellegrino are based around the idea that it's natural for a species to annihilate all other sentient species. The characters define three rules that an alien species may be operating by.
Rule 1. Aliens will believe their survival is more important than our survival.
Rule 2. Wimps don't become top dogs.
Rule 3. Aliens will assume that the first two rules apply to us as well.
[0] https://tvtropes.org/pmwiki/pmwiki.php/Literature/TheKilling...