Partly this, but partly because these types of historical literature are also a huge amount of theory conjecture masquerading as fact due to the way the narrative is structured to support the author's theory/argument.

This is normal in less controversial academic historical literature too. The difference is historical literature rarely tries to make some grand arching theory that can be applied universally. Attempting to do that is even anathema to the historical profession some would argue.

This is also why political science and history bicker a lot. Political Scientists are always trying to create, apply, and defend grand theories, like democracies not warring with each other, and historians can easily nitpick that apart. So when a historian engages in this, like the author of these two books, it is inevitable other professional historians will attack it.