Why would Grandpa chose these folks?
Grandpa likes Mozart but not Tchaikovsky
Grandpa likes Queen Victoria but not Mary, Queen of Scots
Grandpa likes Gandhi but not Mandela
people commonly referred to with first names that is not their real first name
Born: Johannes Chrysostomus Wolfgangus Theophilus Mozart
Commonly called: Wolfgang Mozart
Born: Mohandas Karamchand Gandhi
Commonly Called: Mahatma Gandhi
Born: Alexandrina Victoria
Commonly Called: Victoria
Could it be
Grandpa likes those who came before.
Grandpa likes Mozart but not Tchaikovsky who was inspired by Mozart
He likes Victoria but not Mary, Queen of Scots who was her descendant
He likes Gandhi but not Mandela who was inspired by him.
Grandpa is short so he likes short people