A historical period looks coherent partly because its contradictions have been edited into chapters.

Periods look unified because someone drew the boundaries afterwards. The chapter heading collects things that contradicted each other, ignores the people who did not fit, and produces a coherent age out of a messy few decades. The coherence is an artefact of the editing, and it is very hard to see, because you are reading the result rather than the material.

When a period sounds like it had a single character, look for who inside it disagreed. Diaries and complaints are the fastest route. The same applies to any tidy account of a company, a family, or a decade of your own life.