Ideally, we should judge people based on the merits of their arguments.
However, evaluating the merits of an argument takes more effort than evaluating the confidence with which one delivers an argument. We therefore often use the latter as a proxy for the former. And the latter is a function of the tone of the delivery and how often the communicator speaks in a group setting.
This human bias is unlikely to change in the near future. It’s engrained in us as the result of thousands of years of evolution.
Achieving something at large scale requires not only having the right idea based on its merits, but also convincing many people to work with you on that idea. The latter requires that a large group of people have a positive judgment of you. And that, in turn, requires communicating in a confident tone and frequently.