Yes , It is true that Uttarakhandis living outside the state are more sucessful.
Another truth is that ,not only Uttrakhandis but any person working outside his home state is successful.
Few reasons associated with this can be:-
--When a person is in his comfort zone he has a relaxed tendency towards work.
--When he is outside his comfort zone,pressure to excel brings out the best in him.
--People migrate with a reason, to compete,to excel,to grow and definitely that makes them work harder.
--People will migrate to only those places where there are opportunities and in the process ,his exposure,outlook towards things,perception of people changes resulting in emergence of a more confident personality.
Anti thesis-But then what is the criteria of success,do we just mean financial success?