I always enjoy Wavell Room articles in which career officers share their wisdom about the civilian job market
That is exactly how it is in the civilian world. It's very unusual for the head of a generic support function such as HR, IT, Legal and so on to make it to CEO. The one exception being the head accountant, the CFO.
It seems to vary by geography though. In the UK the tendency is, as you say, for an accountant to be the top man, the US seems to favour legal types and in Germany it is often engineers.
The depth of lack understanding of business in the regular army officer corps is rarely underestimated, exacerbated by a complete unawareness of how wrong they are.