He has a fascinating historical background and is one of the most well known figures in medieval Czech history. Prague has an inpressive statue of him riding a horse. It is huge and on the top of a hill called Vitkov. A neighborhood in Prague bears his name.
He rightfully became a symbol of the fight of the protestant hussites against the catholic crusaders in Bohemia. There is no child in Czech Republic that doesn't know who he was.
The crusades happened later in his life than the part KCD shows where he was just a bandit. Although that part of his life is true too.