Part of the traffic is a function of the fraction of people taking the road, so I can't describe it without using diagrams. However, I remember that it's called Braess' Paradox:

https://en.wikipedia.org/wiki/Braess%27s_paradox

And actually, the example I remember is stated in the mathematical example on that page if you scroll down.

Applied to Musk, the answer isn't necessarily to go back to communicating through managers, but probably just to be more deliberate about designing traffic (communication) patterns when you see gluts happening.