But… I’m going to say the dirty, quiet, and unlikable thing out loud.
That had nothing to do with DevOps or its philosophies, processes, or patterns. That was bad leadership from the top down plain and simple. It’s likely not even the individual engineers faults. It’s leaderships fault for not setting clear objectives, implementing them, ensuring that the engineers had a real plan before beginning, and making sure no individual was too in charge of things.
Leadership in your case was likely career management who knew very little about technical items. Managers who were technical were probably shot down for not playing politics properly, not producing the correct “metrics” and “kpis”. So they moved on.
That’s a company culture issue that has little to do with tech.