IME, "Excessive confidence" is usually a shield for insecurity anyway.
I personally like to see a touch of humility in people I deal with. That, too, can be faked, but at least it leaves you with some idea about whether a job is going to get done.
The worst part is that it actually works - at least on scale.
Bullshit artists thrive on the "they look like they know what they're doing" vibe, because for most people, that level of confidence can only be achieved through hard work and dedication to the craft, so we assume that the person that confident must be very hardworking and very dedicated, or simply knows something that we don't.
It's a perceptional shortcut that we use because it works for us most of the time. In an unknown room full of unknown people, we instinctively search for someone who doesn't look lost.