I have three problems with this argument.
First, it’s not always possible to bet capital. For example, suppose you figured out quantum gravity. How would you bet capital on that?
Second, secrecy is costly and it’s not always worth it to pay the price. For example, it’s much easier to find collaborators if you go public with your idea instead of keeping it secret.
Third, sometimes there is no short-term cost to reputation. If your idea goes against established beliefs, but you have really good arguments for it, other people won’t necessarily think you’re nuts, or at least the people who think you’re nuts might be compensated by the people who think you’re a genius.