We experience and will still experiencing the waves of changes and uncertainty. Will Bitcoin eventually replace Fiat currency? Why or why do you not think so?
You don't have to find answers by yourself as there are many people wanted to find answers for same questions and they spent decent time for finding information, making comparisons and also publishing their reports.Purchasing Power of the U.S. Dollar Over Time
How is the 21 million bitcoin cap defined and enforced?
Their difference is not coincidence of anything but comes from their big differences in total supplies, circulating supplies and inflationary rates over time as shown by following charts.
Bitcoin Supply Inflation.
