Dave,
How do these people know these thing? I'm gobsmacked.

Historians derive their views from the results of years of research Dave.
They challenge each other to justify everything they say.
Unlike you, historians do not regard it as acceptable to express an opinion that they can not support with hard facts.

Not being an historian, I form my views by reading history books.
That is what intelligent people do.

You must have a huge ego to imagine that you know better than the history books, and the historians who research and write them.