Some early adopters own large amounts of Bitcoin because they risked their time and resources on an unproven technology that was barely used and harder to secure. Many early adopters often spent large amounts of Bitcoin or bought small amounts before Bitcoin became valuable, and therefore did not see huge gains. There is no guarantee that the price of Bitcoin will go up or down. It is very much like investing in an early startup that may gain value as it becomes more useful and popular, or it may never break through. Bitcoin is in its infancy, and its designers took the long view; it is hard to imagine how it could be less biased toward early adopters, who may or may not be tomorrow's early adopters.
