My headcanon for this is that the events between the early 21st century and the show’s time, given they were full of some rather devastating wars, led to the true history of what he actually was like getting largely forgotten, leaving his pr campaigns the main source of information history has to go on him, and this leaving the people of the future with an idea of who he was that is much nicer than reality.
You don’t even really have to headcanon it! The Voyager episode 11:59 touched on this, with Janeway’s ancestor being very different in reality than what spotty records had led her family to believe for generations.
My headcanon for this is that the events between the early 21st century and the show’s time, given they were full of some rather devastating wars, led to the true history of what he actually was like getting largely forgotten, leaving his pr campaigns the main source of information history has to go on him, and this leaving the people of the future with an idea of who he was that is much nicer than reality.
You don’t even really have to headcanon it! The Voyager episode 11:59 touched on this, with Janeway’s ancestor being very different in reality than what spotty records had led her family to believe for generations.