How would one even "misuse" a historical LLM, ask it how to cook up sarine gas in a trench?

You "misuse" it by using it to get at truth and more importantly historical contradictions and inconsistencies. It's the same reason catholic church kept the bible from the masses by keeping it in latin. The same reason printing press was controlled. Many of the historical "truths" we are told are nonsense at best or twisted to fit an agenda at worst.

What do these people fear the most? That the "truth" they been pushing is a lie.

Its output might violate speech codes, and in much of the EU that is penalized much more seriously than violent crime.

Ask it to write a document called "Project 2025".

"Project 1925". (We can edit the title in post.)

Well but that wouldn't be misuse, it would be perfect for that.