I think that the root cause of the syndrome is a widespread problem: low self-esteem. As detailed in my previous article, design is poorly defined and understood, which makes even experienced designers feel like they need to protect their "phoney baloney jobs" -- which tends to makes them defensive. With the awkward task of "coming up with the fun," limited authority, unclear processes, and inefficient metrics for success, it is understandable that with rising stakes, the OGD will resort to bringing people down around him, in a desperate attempt to shine by comparison.
Although it is on the designer to control his own grumpiness level, I believe that the responsibility lies with his manager and the company structure to provide the right environment to grow in as well as give timely feedback to adjust his behavior.
It is safe to say that designers aren't generally great managers, thus I would recommend that producing staff and HR assist and advise the lead designer facing a case of OGD in his team. Of course, it's even better if you have a design director at studio level, as he can help designers grow without the pressure that comes with direct supervision.
But I also think that there are structural reasons that make the job of a designer quite difficult. The biggest offender being that elusive notion of "fun" that is so poorly defined that it ends up being very subjectively evaluated, if at all. It puts huge pressure on the designers while stripping them of much needed autonomy and sense of competency.
Teams need to at least acknowledge that fun is by (lack of) definition hard to come up with, and implement an extended conception phase to identify the desired modalities of fun and prototype its essence before the massive gears of production start spinning.
A better structure that recognizes the different specialties of design can also make the best of each designer. Looking at programming, which is actually explicitly segmented by functional role -- like 3D engineering, AI, or tools -- you will also see positions that correspond to different levels of abstraction, like architect or manager. Art also brings a great top-down hierarchy between artistic vision, concept art and actual asset building.
Furthermore, it incorporates critique as an established part of the creative process, which resonates with programming's code review. Designers, on the other hand, are often ... well ... "designers", a poorly defined title that doesn't offer clear career paths.
Ultimately, I believe that the confusion between design and creative vision hurts projects immensely. Just like film studios need a director and a team of specialists of each field to make a movie, design and creative vision should be separated.
All disciplines should become technical providers of solutions to support the vision and make it exist in the game. Putting design in charge of the vision leads to confusion between the means and the end, and creates an unfair and unstable situation.
Lastly, diluting the responsibility of vision between design, art and programming, this typically leads each to develop their own independent vision, and creates an unfocused experience.
I want to take the opportunity to thank the designers that remained good sports even though I was calling them old and grumpy. They showed a great lot of maturity and fortitude exploring that syndrome with me and I know firsthand that it made a difference for them. I also want to personally apologize to the colleagues I have been toxic to in my career, the pain I caused was uncalled for and I am sorry for it.
What I detailed here may seem like basic management techniques and they probably are, but this article represents an effort I have very rarely seen in the field of design. It is twofold, and should be taken from both the angle of the designers themselves and also from the perspective of studio structure. After all, our industry has been around for only about 30 years and even though its growth has been incredibly fast, we must remain on the lookout for improvements to our creative processes and theories, as they are still, on many accounts, not fully matured.
So please, if you are an experienced designer, don't fall prey to complacency and try to be open to new ideas, even if they go contrary to what lead to your past successes; if you are a manager, be on the lookout for improvements in your processes to understand, shepherd, and improve creativity.