The pope chooses his name or may even wish to keep his birth name. It is not required for him to choose a new name.
There has been no pope named Silas.
There is no pope named Pope II.
"They" did not change the name of the new pope, When elected, the new pope has the choice of keeping his Christian name or choosing a regnal name that he wishes to be known as while serving. When Christ named Simon as the first pope he changed his name to Peter. After Peter, the next pope to choose a new name was Pope John II who was elected in the year 533. His given name was Mercurius and he did not think it proper for a Catholic pope to be named for a pagan Roman god - Mercury.
There is no pope named Eberhardt.
There was no pope named Claremont.
There was never a pope named Lexo.
There have been 13 popes named Leo but no pope named Leonard.
No, there was never a pope named Alexander Sexton. There was also a Pope Alexander Sextus meaning Pope Alexander the Sixth (VI).
There is no pope named Pope XXIII. If you are referring to Pope John XXIII, he became pope in 1958.
The Pope is not always named John Paul, there are only two.
Jesus Christ named the first pope and changed Simon's name to Peter.
No pope has chosen that name. There is no prohibition to a pope using Matthew.