Why is a job interview needed if I am the only suitable candidate for a research-assistant position? I have recently applied to a research-assistant position at a university in the European Union. I got admitted into the interview. However, I am the only suitable candidate to this job, as I could see by the official documents.

I have several doubts about this situation:


Why would they want to interview me, if I am the only candidate, and they find me suitable for the job?
What type of questions/discussion in the interview should I expect? It is a fact that I am not facing any competition, so what will the purpose of this interview be?
Is there any chance of not getting the job? I am really interested in the job, and I did not lie about anything on my CV. Can I still be considered not adequate for the position?
Is the interview just a formality? The original job posting says that the evaluation methods are curricular assessment plus interview thereafter.
There are a few possibilities. 

It may be that an interview is required by the policy of the institution. 

It is also likely that they want to get an idea of how you would fit in personally. If they are happy with your application materials and have no reason to doubt your honesty in that, they just might want to know if your personality seems compatible. 

Yes, it is possible that you don't get the job. If they decide you are a complete jerk (sorry, nothing implied) they won't want to hire you and will most probably restart the search. 

But, I'd advise that it isn't anything to worry over. Just be yourself and use the interview to help decide if you want to work with them. If you decide that they are complete jerks you will want to keep looking. 

They may want to quiz you on aspects of your knowledge that are especially important to their work. Be honest in your answers, even if you aren't familiar. Be positive, of course, about your abilities and adaptability if that seems appropriate.