Question

Why did the people call Einstein a world citizen ?

Answer 1

because he is famous and talented person
einstein's brain is preserved in a museum
he found e=mc2 formula
he got many awards
but his mentality is childish mentality
his brain works more than a normal human brain

Answer 2

because his brain is very big and different to other common human being..

he is very intelligent also.

and he gives theory

E=mc2