And that's normal.
As we learn, as individuals, communities and societies, the best of the previous generation becomes at best the SOP for the next generation. Assumptions and norms shift. What was acceptable yesterday is not today.
And that means the leading citizens of one century, become pilloried slaveowners the following. That the edgy jokes of one generation are the Dad jokes of the next.
The image of Queen Elizabeth viewed through a post colonial / imperial lens shifts. Our perception of President Kennedy regarded through the moral values of today distorts the figure from history. Jack Welch goes from corporate superhero to dinosaur as the policies he pursued - cutting edge in his day - are discarded as no longer fit for purpose. The list goes on.
Marx (Karl or Groucho), Mao or Catharine the Great, Bolivar, Cleopatra or Boudicca all lived - well or not - according to their time. Viewed by a different time (or culture for that matter) how they lived can look very different.
So next time you find one of your heroes has feet of clay, ask yourself how your values and context are coloring your view of them.