[maximinus_thrax]

> ever been promoted to an engineering manager

Your first sentence is a red flag for me. This is not a promotion. If you think this is a promotion, you've already failed. If the org/company thinks this is a promotion, they need to work on their culture.

This is a new job, with different incentives, different skills, different responsabilitites. Thinking of this as being a promotion already poisons the well as you're considering yourself 'better' than the ICs you're supposed to work with. Stressing the 'with', as a promotion implies they'll be working 'for'.

To answer the original question, this happens all the time. In my current job, our manager left for a different company. An IC was handpicked to lead the team (basically a puppet of our M2). They found out in 6 months they don't want to do this anymore. No big deal, they've communicated this to their manager and assisted the org in hiring a new but experienced manager. It took another couple of months, but there was no harm done.

Just talk to your manager. Tell them you don't think you're a good fit for a management position at this time in your career. As you're a new manager, they will definitely have a plan B for this.

Good luck.