Good communication skills are certainly essential to being a con artist, but they are also essential to working with other people who are almost certainly going to be very different from them. If someone is incapable of explaining something to another person or discussing and agreeing on a course of action, that's somebody who probably doesn't know a fraction of what they think they know.

For every gregarious person who uses their communication skills to fake competence, there's at least one person who is convinced that they are a misunderstood genius, but their lack of supposedly BS communication skills has cursed them from ever being fully appreciated by the "normals" that they think they are better than. You don't want to be either one of those people, they are equally useless when working on hard problems.