Side-stepping the issue of whether rationalists actually "win" or "do not win" in the real world, I think a-priori there are some reasons to suspect that people who exhibit a high degree or rationality will not be among the most successful.

For example: people respond positively to confidence. When you make a sales pitch for your company/research project/whatever, people like to see you that you really believe in the idea. Often, you will win brownie points if you believe in whatever you are trying to sell with nearly evangelical fervor.

One might reply: surely a rational person would understand the value of confidence and fake it as necessary? Answer: yes to the former, no to the latter. Confidence is not so easy to fake; people with genuine beliefs either in their own grandeur or in the greatness of their ideas have a much easier time of it.

Robert Kurzbans' book Why Everyone (Else) Is a Hypocrite: Evolution and the Modular Mind is essentially about this. The book may be thought of as a long-winded answer to the question "Why aren't we all more rational?" Rationality skills seem kinda useful for bands of hunter-gatherers to possess, and yet evolution gave them to us only in part. Kurzban argues, among other things, that those who are able to genuinely believe certain fictions have an easier time persuading others, and therefore are likely to be more successful.