Most of the crypto startups use .io domains,so I would say that .com domains aren't important at all.
If you are asking about the brand-well,it's important but the idea behind the project and the dev team are more important.
How do you know for sure the majority of a legitimate crypto startup project is using .io domains, it is based on assumptions or data. Anyway, I'd agree that the ideas and concept behind the project are far more essentials than a domains name. You could achieve better if you allocate a significant amount of fund to research and development sector.