Sun Life Case Manager interview questions

I found the human resources department to be incredibly disorganized (offering me an interview then forgetting to provide a date/time) and the interview itself to be incredibly uncomfortable. One of the two ladies was somewhat friendly - the other (apparently the woman I would have been working under) was plain rude. The interview itself lasted only 15 minutes and at least 5 of the questions were about why I was looking for a new position. No behavioral questions, no questions about my work ethics or personality. I felt on the defense for much of the interview, explaining why I was applying outside of my current company. I was absolutely shocked to receive an offer and felt I had to turn it down.... How can I justify leaving my current job to work in an environment like that?