Often the person doing a more complex or impactful job has a lower wage than a new junior coworker. This can happen with employees that have been at the company

Often the person doing a more complex or impactful job has a lower wage than a new junior coworker. This can happen with employees that have been at the company long, whose wages have stagnated. When a company hires new people at current market rates, those new people will have a higher wage, for what can be the same or 'easier' job.