I have googled but didn't find. "A person who gets interested in anything very quickly and loses interest in it sooner." What is such a person called?
Not necessarily a butterfly mind, but just a butterfly.
butterfly (The Free Dictionary):
2. a person who never settles with one group, interest, or occupation for long
butterfly (MW dictionary):
2 : something that resembles or suggests a butterfly; especially : a person chiefly occupied with the pursuit of pleasure
2 a person who flits aimlessly from one interest or group to another: a social butterfly
One might describe such a person as a dilettante, in the first sense:-
a person who takes up an art, activity, or subject merely for amusement, especially in a desultory or superficial way; dabbler.