What does 2 Samuel 18:18 mean?

While he was alive, Absalom had set up a monument for himself in the King's Valley, saying, 'I have no son to carry on my name.' He named the pillar after himself, and it's still called Absalom's Monument today. 2 Samuel 18:18 - Modern Text Bible

(Absalom tried to secure his legacy with a monument, knowing he had no sons. It's a sad irony, given his shameful end.)