Quartus Engineering Optical Engineer interview questions

Started with a phone inteview that went really well. From there moved to an on-site interview that lasted 6 hours. Everyone was very nice and professional, but it felt like halfway through the day they had decided I wasn't the one they wanted. I flew back home and waited to hear the results of the on-site, but I never heard from them again. It's one thing to not be a good fit, but it felt very unprofessional to be ghosted by a company that prides themselves on being first class.