For sake of argument, have you considered selection bias or cause/effect reversal as another explanation?

What I mean is, perhaps the people who are able to clearly and concisely explain their ideas are the ones who are most likely to become senior engineers, managers, etc? As they proficiently share their ideas, they tend to have a lot of influence, which in turn leads to them getting promotions. Communication and interpersonal skills are a huge part of being a good engineer working on a team.

There was a guy I worked with when I was a new grad, let's call him Bill. Bill himself was also pretty fresh, had a few years under his belt maybe. But Bill can communicate with a level of clarity that I am still in awe of. Of course he became a senior engineer while he was very still fairly young, and of course he has a lot of influence. The technical skills to become a Senior Engineer are only half of the equation.

I say this all as a (non-senior) engineer who finds he often has a hard time with communication and interpersonal skills. I'm growing technically, but I've got to work way harder to grow those soft skills at the same rate.