Super Micro Computer, Inc. (Supermicro) interview questions

There were four interviewees comes one by time to interview me. The total procedure lasted 3 hours. The first interviewee talked with me a lot about my resume. Most questions were about the resume, I explained in detail. The second one asked me some easy professional knowledge. which were basic in electrical engineering. The third one talked some his experience, easy chatting. The last one also asked me professional knowledge, and gave me several problem let me explain. Then it was over. I felt very comfortable during the interview, the four managers are kind and nice. I think they want to find a person who may not that professional, but have to be nice working with. After 3 weeks, they said they couldn't give me offer because they could not sponsor H1B Visa application. I pointed out my visa status on phone interview, and in the whole process of on-site interview, at that time they didn't mind it. But at the end, they refused me for the reason of visa status. Waste a lot of time.