I did not seen all that much promotions based on technical competency. We promote based on impressions of upper management that have zero to do with technical competency and zero to do with leadership ability.

Also, pretty much all non technical lower level managers were disaster. And issue was not just their lack of tech knowledge in pure form, but their insecurity, inferiority complexes and what not everybody else had to deal with. And profound not understanding of culture around tech just lead to completely unnecessary misunderstanding.

Lack of technical knowledge in the context of managing technical people imply that you will fail in social aspect too.