Both the people part _AND_ the technical parts are the hard parts of technical management.
Of course some domain knowledge is needed.
My anecdotal experience with manager is either : they are useless and will rubber stamps things. Or they are actually involved, then, you want someone that has a vague idea of the process of doing the work. I vastly prefer someone who has produced code at some point. It’s fine if it was 10 years ago the last time it happen.
They need to build and facilitate a team to be run by itself and arbitrate on difficult decisions, sell team, etc, etc.
It's easy to say that something that seems simple when explained in simple terms is easy or quick to implement, but the people 'at the coal face' are often all too aware of the implicit complications of the task.
Also, you’re going to be manipulated and hoodwinked by the managers around you who are technical.
Lastly, the engineers you’re managing are going to laugh at you behind your back.
I’ve seen all of this happen before.
The interesting parts start to pop up when you need to make difficult choices. Good managers with a technical background are scarce and therefore not usually available. Sometimes you need to make a choice between a bad manager with a technical background, a good manager without a technical background and no manager at all. Whichever choice is made, it will never satisfy everyone.