Volvo Group Reliability Engineer Co-op interview questions

Submitted an online application. A couple of days later I recieved a phone call by the hiring manager and they asked me a few questions about what I have been studying in college and my interests in this field. I gave a very brief discription about my studies and only went into detail about the energy audit project I was currently doing. The manager said I will hear something from HR. I didn't recieve a phone call or an email for about 6 to 9 weeks. Then HR called me and asked if I was still going to start on the original start day given. They talked as though I had been hired this whole time; however, this was confussing to me. I had a background check and a hair examination drug test. I believe that took about 4 weeks for the result of the background check.