Clearly your bosses disagree and decided that this new guy had some value or skill set that you do not. Maybe there were some behind the scene politics, or maybe they wanted somebody with more ambition who didn't just sit and wait in the junior position assuming they were a sure bet for promotion when senior production manager retired.
He is telling a whole pack full of lies, though some of them may be honest lies. He's lying about only making $20K/yr unless his venue is only part time, which is possible.
He's been working six years as the manager of a single concert venue? That would tell you why he didn't get it right there.
One reason is that acoustics is set up in most venues in less than two hours, which used to be a big part of the deal. Now, a reading can be taken periodically, but essentially one performance can use other performance readings to set up their equipment. It's much easier.
Second, what used to be bundles of cable and an entire crew to set up and tear down is often down to some CAT-5 and fiber optic cable, and a company installs it once and leaves it, only changing things if a line goes bad.
Third, Acoustics boards themselves are now digital, and once complex changes can now be preset. The same is true for the lightboards and they can both be routed to one computer or more and controlled without much skill.
That being said, there is a need for venue concert events managers, but they need somebody who knows how to setup everything from a stadium or outdoor concert, to a concert in a bar, to a concert in a hotel. There are a lot of other things that they need to know as well.
In a way he stood there and let himself be fossilized, and I can sympathize with that. I'm playing a game of catch up, myself.