Boxes are checked on all jobs. Some situations don't have or need 3 candidates and life ain't fair. A person make check all the "qualifications on paper" boxes, but candidates also need to be vetted- this is where a lot of folks miss out. If your personality/character sucks; you mistreat student-athletes/folks around you; undermine leadership; have an inability to discipline/control the athletes you are over; can't follow rules, etc. etc. also plays a part. So being the most qualified doesn't automatically mean you should bag the job. Coaches/ADs are always watching- so how you represent yourself definitely plays a part well before you apply for that future job.
Bringing a particular number of candidates to campus is at the department's disgression. Some school's HR dept are like- if you know who you want, you don't have to bring them in- " Just let them know the terms of the contract and they'll get the hiring process started!" Hell, most interviews happen at championship meets and conventions anyway. Which is why if you want or need a job, you go- even if you don't have athletes in the meet- to be seen and chop it up.
If you or some uber-qualified person you know keeps getting passed over on jobs- the common denominator is YOU.