Sourth America has not taken down statues of Simon Bolivar, the liverator of many countries, Che Guevara is still revered in Cuba.  Imagine America without George Washington or Abe Lincoln.  Statues, schools still carry their names.
By taking down statues of Tribhuvan the maoist are trying to erase the memory of Nepali history.  Or maybe they are trying to make way for Dalal and Bhattarai stuatues.