It's not always about the capital but capital does play an important part in your ROI. Just having the capital isn't enough reason to expect more ROI, your duration of investment also matters and your market entry too because you can't be investing late and be expecting a more return than an investor that entered the market when the market was at its lowest price unless you'll be willing to spend more. Investing in Bitcoin at $30,000 isn't the same thing as investing at $60,000 If both investors had the same capital. The investor buying at the first price would make more profit if both investors are to cashout during the same time.
Investing isn't all about the capital that you have at your disposal because there are certain investors that have the money but lack the knowledge and aren't doing well in the industry. People are losing money frequently when the market takes a dip because people are closing their position without second thoughts. There are things that makes you a successful investors and capital isn't one of the most important because you can have the capital yet you don't know how to use it. Having the right knowledge is what is more important than having capital because a bonus and makes your investments much easier.