You're confounding descriptive and persctiptive theory. Such conflicts are an obvious consequence of the setup despite deeper strategic analysis advising against it.

In his book, Mearsheimer

> readily acknowledges the inherent pessimism of offensive realism and its predictions because his world is one in which conflict between great powers will never see an end. [1]

1. https://en.m.wikipedia.org/wiki/The_Tragedy_of_Great_Power_P...