ATC’s have always had an age cap because the job is considered so stressful.
I know. I got an ATC job when Reagan fired the strikers. But I turned it down for a promotion and large raise not to leave the company I worked for. I did the right thing and have never regretted it. I took a golden parachute years later rather than relocate. I’ve done even better since then. As for stress. Most ATC jobs away from the huge airports are more boring than stressful.