The demand for the nMP "was" high... during the initial release.
No one in their right mind would spend the kind of money they charge now for a nMP in 2017.
Everyone knows this.
There's also been multiple tech news outlets denouncing the Mac Pro as obsolete. I'm pretty sure Apple got a wind of those reports.
The other problem is that Apple no longer has a dedicated division for Mac-related tasks. They now have to cooperate with iOS teams. Problem is, iOS gets way more priority than the Mac does.
Tim Cook is an operations and logistics guy, not an innovator...
Apple desperately needs a visionary to be at the helm of the company.
Sad thing is I don't think there ever will be.