Typically, the hiring decision is made by the person the position reports to. They'll have a salary cap to adhere to, which is certainly too low, which means the employee who is willing to take the position is likely underqualified or incompetent. It may also be in the hiring manager's interest to fill the position with someone less competent for a variety of reasons. You don't want the candidate to be good enough to have the opportunity to job hop right out in nine months. You don't want the candidate to be someone who would challenge your decisions and put your own job in jeopardy. Maybe you just need a warm body in a role immediately, fully intending to fire them when you find the "right" candidate, and then just never do that.

HR just does the paperwork.