Studying why people are unhappy in their jobs is worthwhile so that people can learn how to find jobs that they are happier in as happier workers tend to be more productive.
I'm not sure I agree with the conclusion though. Personally I find that my best managers were the ones that had little or no technical ability in the realm of what their staff did. They also happened to be the ones that actually understood the role of a manager and managed the team/projects on the whole rather than trying to get into the details. All the "knowledgeable" managers I've had fall into two equally bad (to me) categories. The first really doesn't know as much as they think and make life more difficult by injecting bad or wrong information into the process which (at best) drags things out or (at worst) makes the whole team look like a bunch of idiots that can't get their stories straight. The other group is those that actually do know their stuff, but they fall back to just doing it themselves rather than managing their team to get things done.
The real key is that the staff has to trust the manager to stay out of the low level details and the manager has to trust his staff to actually be competent at their jobs (and if not, do something proactive about it). Without the trust and everyone sticking to their actual role it all falls apart and people are miserable.