You can't really avoid hindsight if you know anything about a historical event. This is just fine if you are writing about history, where you want to know what's really going on, but if you are ripping off history for fun and profit, it's a problem, because there, what you want is to know what the people thought of it at the time.
They didn't know that the heir to the throne would die in childbirth. They didn't realize that the king would die young. They had no way to know that a politician's abrupt change of rhetoric was purely strategic and did not indicate a change of mind in the slightest. And realizing what it meant to think like that is the key to getting inside their heads, which is what is really needed to rip off the era for characterization tricks.
Reading between the lines is even more fun when figuring out what it is that the writers are taking absolutely for granted.