> The manager at my structural engineers can still calculate a beam size, he is better at it than his staff. So why in software should an engineering manager move away from tech...

Because a manager at a structural engineering company is essentially acting as the equivalent of what a Product Manager or Forward Deployed Engineer is in the tech industry, because they are expected to be a technical domain expert and own delivery.

Meanwhile, for most software companies the underlying codebase isn't want generates revenue - it's the codification of business logic that does. Additionally, companies tend to have a separate Princiapl Eng to Distinguished Engineer/Architect track that outranks EMs and is in direct contact with leadership.

> Is it this MBA idea that management itself is a profession, rather than being 'a higher level thinker than the others'

Most Engineering Managers and Beancounters aren't MBAs - no company wants to sponsor an employee at a PTMBA which can cost upwards of $250K now.