Enstoa .NET Software Engineer interview questions

I was talked to their HR manager about my background over the phone and also talked with their vice president. and they gave me a case study to resolve, and I was submit the result and they invited me to onsite interview. The interview on their office was pretty easy. but I was wondered that why they invited me to the onsite interview. because almost of interviewer who assigned to that interview was on vacations. they had to reschedule the interview. I had the interview only with 2 of their associate developer, which was very easy.