The finished monuments present a political right of that specific time period
The starting point of the transformation was the Wars and the political change during the 20 century.
A counter monument is a new form of memorial. The artist tends to restore the event rather than making it into a public art.
The public and the government in the 20th century are expecting more monuments with traditional form, but the contemporary artists are putting more personal reflections into the monuments.
I think in the 21st century, monuments are strongly tied up together with contemporary art. More forms of monuments are accepted by the public and the government. The artists had less limit, therefore the monuments are more abstract and ornamental. The monuments nowadays are not only serving the purpose for the public to remember a historical event, but sometimes also makes a landmark, brings an atmosphere to the public area.