It's fairly wild to see within my own company as well.
Used to be a smaller trading firm, global firm but still office was small, 200 - 250 people. 70% traders. Now, office has grown to 500 people or so, maybe 30 - 40% traders. Rest are HR nonsense or similar positions which can barely be associated with generating revenue.
Those nonsense positions hire more nonsense positions until, as you said, they are deeply interwoven within the company and therefore have control.