If Clinton is the best candidate to serve the average American's interest, why is she the only one taking large donations from Wall Street?

If Hillary Clinton is the best candidate to serve the average American's interest, why is she the only one of the four running who is taking large donations from Wall Street and corporations? Wouldn't this be biting the hand the feeds her if she went against her large donors? Plus, Wikileaks revealed that her public positions differ from her private positions and that she admits to being away from the middle class as well as advocating for what is best for the elites.