(Edit: I wrote this and then realized you are a historian. Leaving it because maybe other people want to know one way of relating history to other fields).

Some thoughts about distinguishing historical research from other research and why it might be valuable.

First, history is exceptionally method agnostic, compared to other fields. Non-specialists (journalists, bankers, English professors) have made major historical contributions. This isn't because the methods used are always basic or non-scientific, but because such a wide variety have proved useful for historians. Historians usually can't go back and gather more information from their subjects, so their methods have to be flexible and change based on the time and place, and trying to define the 'historical method' is a pretty nebulous task. It's something sort of like, 'what evidence exists about this subject&period&place, and what can I trust it to describe accurately?', and then you choose whatever tools from other disciplines make sense to answer the question. This is a pretty Bayesian-friendly mindset compared to other fields.

Second, other disciplines usually begin with an 'object' that they can then apply interpretive methods to, or an object which they can conduct tests on in order to test a theory. Historians, instead, mostly construct historical objects. Most historical questions start as "what was going on with X?" or "why do these other historians disagree about what happened during X?" "How do we periodize this series of events?" and the answers will be "England was developing a working class" or "military records and civilian correspondence tell very different stories about the Civil War" or "there seem to be six distinct stages of US party politics."  Sometimes two historical objects are so closely entangled that it's hard to study just one (how can you understand the Haitian Revolution without knowing what was going on in France?), and it's probably good that historians can tell other researchers that.

So here are some things historians might do, according to me:

1. Integrate extremely varied types of evidence into coherent estimates, for example, of economic measures in Rome. Without historians interpreting the reliability of partial and political sources based on a deep understanding of ancient Roman society, economists might have to sift through a lot of unreliable data or just give up.
2. Summarizing the most significant factors, in the form of top-level narratives, affecting a specific subject&time&place. It's pretty essential to understand the historical context of a country or other object of study, if only to understand confounding variables, before attempting to test hypotheses. Such birdseye narratives are a pretty fertile ground for developing hypothesis that other fields can test.

And some things which are probably not history in the strictest sense, even if they rely on a lot of historical work, according to me:

1. Extracting general features of what causes civilization collapse, based on how historians describe specific previous civilization collapses (this is probably most accurately anthropology, but social science is messy).
2. Evaluating whether the effect of specific mining systems on land tenure can explain why mining systems have a long run effect on poverty, using a natural experiment in Colombia & Peru between the 14th-19th centuries (which is probably economics).

I would be kind of shocked if historical research, in this fairly strict sense, was directly action-guiding. Yet for EA, a lot of historical research might still be valuable, mostly by creating & consolidating the body of evidence available for other EA-focused research. For example, describing more clearly the impact of technological developments on women's labor, or cataloguing the salient details of past near-civilizational collapses, or providing overviews of social movements.