a) you do not know if he or she is not wealthier than one of them (or if he is one of them)
b) the listed people had different profit gaining careers which are not necessarily only based on financial trading. For example, Bill Gates started a software company and got a large loan from his parents.
c) In a large enough group it is statistical possible that players with the same capabilities, but subjected to a random environment will end with different amounts in the end.
d) Also if the average advisor is not better than a random generator then there still can be an advisor or player who is better than average who will earn a fortune.
e) To get really rich, you must understand the financial market. but you also need an advantage by having a special insight in the market and most importantly politics (as politics define the rules of the game).