It's combination of following:

A. Real hard work (if someone has not taken the shortcut for passing OCP)

B. Previous IT experience, particularly any kind of Database related exposure, does not matter whether it comes as a Developer or anything else

C. Presentation skill during the interview to give a reasonable comfort level about your abilities. I am not advocating to "misrepresent" during the interview but present the facts in more appropriate way so that it gives an impression that even though one is not having a real experience, he/she is ready to take on challenge.

D. Good fate to get a break

E. Ability to apply the knowledge in the job, also learn from mistakes and see how others are doing the work. Refer to many books, forum and any other source to see how the same work could have been done. After all DBA WORK IS NOT A ROCKET SCIENCE, it is a responsible job but with cautious approach one can definitely acquire the skill.
Remember one day each DBA had the same state as a new entry level DBA has. In fact things have become much easier for anyone to start as a DBA in present times with so much of resources available on internet and books.

F. Imagine, imagine and imagine about different scenarios in database and try to find a solution beforehand..a kind of proactive approach so that one is ready before problem hits.

I generally speaking would like new DBAs start in the above way. There are many who feel that DBAs can never be born and they come from a different world!

However, I must say that the reality is a far cry from the above, new DBAs are trying to take a shortcut approach. In the long run that shortcut approach is not going to help. Also, there are old seasoned DBAs who are not changing with times and have stuck with the old concepts and they are the ones who feel perhaps insecure and do not want to see the new DBAs coming in!