Nautilus Solar Energy interview questions

There were three rounds of interviews that I went through. I felt like every interview went well, as each person had very positive things to say about me after each round. However, this was cut short because, after the third round, I was completely ghosted. Despite continuously following up with each person I interviewed with (none of whom responded, by the way), I finally received an email stating that they had decided to fill the position internally instead. I found it very unprofessional and discourteous not to have the decency to at least reply to my emails to let me know what had happened.