Smaato interview questions

First round interview was with HR, then Hiring Manager. After that I got a case study. After that I had an interview with the Director. HR came back to me and scheduled another unplanned interview with head of another department without any context or description of this interview. The questions on this interview was deeply technical more than the job requirements and the expectation. After that they completely ghosted me and ignored my follow up emails. after 11 days I got the rejection email.