Lewis knew nothing about politics - he did not bother with it - and studied little history. He liked the classics, literature and religion.
But his political insights were excellent, and his futuristic novel far more accurate than those of other - apparently better informed - writers.
In fact, he wrote an excellent book on how to read literature in its historical context:
Medieval and Renaissance Europe had politics that make our current practitioners look like a church committee. Machiavelli simply summarized it all.
I agree absolutely about Lewis' insight -- but you can't read Tacitus and Livy and Geoffrey of Monmouth and Snorri Sturleson and come away without a knowledge of history and politics.