An example: His idea that Ukraine should give up territory to please Russia made it clear that he don't understand modern Russia or Putin. It's not a conflict in which he has no relevant experience or any deep insight, yet he felt the need to use his influence to present his poorly thought out idea.
Had he stepped back from the public 20 years ago, then may the majority of at least Americans would have remembered him as a great statesman, but he need to be heard and saying stupid shit has made people more aware of his past and his terrible actions.
And yet it is exactly this behind the scenes that Ukraine European backers are pushing Zelensky to do. When it is clear that the war is a quagmire and Ukraine is underperforming.