As a (former) team-lead and engineering manager (now back to working as an IC), I can say, to paraphrase Edward Gibbon, that management is seldom of much efficacy except in those happy dispositions in which it is almost superfluous.
After suffering a mass layoff last year, one observation points to explicit and endemic ageism:
All my former colleagues and reports 15-20 years younger than me landed jobs within a matter of months. Those of us 50+ remain unemployed a year later. It isn't about skills; I was at the top of my game when a layoff robbed me of my livelihood. It isn't a matter of pay. One of my former reports whom I mentored when I was a senior IC left right before the layoff hit with a job offer making as much as I was at the time as a manager.
It was even explicitly revealed to me by an insider and former colleague who referred me to one position that I didn't get that the hiring committee wanted to go with someone younger, after which he caught himself and backtracked saying "earlier in their career". I was told on another occasion that I'd make a great addition as a manager or principal IC, but that they were reviewing their needs and deciding to search for someone less senior.