I went through all 3 rounds of the interview process (HR, 45m technical interview with the department head, 3 x 45m technical interviews with 3 different employees). After completing all interviews, the company suddenly ghosted me. After 2 weeks of waiting I messaged the lady who contacted me initially via LinkedIn for any update but received no response at all. After another week, I messaged the HR rep who scheduled all the interviews and received no response either. I thought they may have been hit with layoffs but I saw how both individuals have been plenty active on LinkedIn. I think it is very unprofessional, especially from a company of this size to have someone prepare and undergo multiple hours of technical interviews as well as the initial phone interview while they are still employed and have to make availability arrangements only to be completely ghosted afterwards. This has never happened to me throughout my career. Ironically, I have recently accepted an offer from one of their direct competitors.