'A new hire got a promotion over me. I'm lost as what to do': Employee gets passed over for promotion because they're too valuable in their current role

There's this idea that sums up how we end up with so many incompetent managers, which is called the "Peter Principle." You've probably heard of it before, but if you're just coming across the term for the first time, it's basically surmising that people who are good at a job get promoted to the next level, even if that promoted position really has nothing to do with the skills they've proven to be apt at. What's unfortunate about these situations is moving into management is really the only way to advance your career and eventually move into a role where you're finally compensated at a livable rate. Productive workers just aren't recognized or paid fairly in this day and age. So, the necessity to move up the chain into management means more and more people who shouldn't and probably don't want to be managing people end up reluctantly attempting to do so. 

Say someone is working at a paper company as a salesman; they're the absolute best at their role, outselling all other salesmen 2 to 1. They're a little bit of a dunderhead, but they're so effective that they get promoted to management. This is exactly how you end up with managers like Michael Scott from the office; you've probably encountered one or two in your life… What this fictionalized example doesn't show you is how, after spending years in this position, the "Peter-Principled" individual becomes increasingly toxic and set in their ways, frustrated at their lack of advancement and gripping increasingly onto 

It's also true that the reverse of the Peter Principle occurs when a productive worker is recognized as being so effective and indispensable in their role that their superiors refuse to promote them, knowing that doing so would tank productivity. Still, they refuse to pay them a rate that matches their experience and productivity, somehow simultaneously taking their experience for granted while they get passed up for promotion after promotion until they give up and leave.

That's what seemingly happened to this worker who was passed up for promotion in favor of one of their less experienced coworkers, turning to this online community to vent their frustrations and spark discussion on the topic.