If I was a hiring manager who set up a hiring process to evaluate candidates, and someone did poorly on it but the CEO came and said "no no, hire this person anyway, I know they failed but it's fine" I would quit.
If I were a CEO trying to build a successful company and found a willing competent worker, whose hiring would fail because of the hiring manager's ego and inability to adapt and do what's right, I would consider it a purposeful sabotage and would fire the drag-downer.