Many wealthy people do start from nothing and make their fortunes, and many wealthy people simply inherent their fortunes. The majority of wealthy people, however, start from neither the very top nor very bottom, but instead work hard from somewhere in the middle (or upper middle) to where they end up.
Super-wealthy people earn their money by making smart financial moves. Whether through investing or hard work or both, rich people often make their own fortune. The only way to make a fortune without trying is to be born into an independently wealthy family and inherit a ton of money. Rich people generally have to work hard and make sacrifices to earn their wealth.