MOSAIC Software Data Engineer interview questions

Got a call from HR, scheduled and online interview. I solved all the algorithm and SQL related questions without any errors. The interviewer gave a positive feedback and said that he liked the way I explained the coding process and of course the code was correct so, he was pretty happy. 5 days later, when I follow up, I am told that they have hired some other engineer who accepted the offer and rejected me. WHY ON EARTH DID YOU WASTE MY TIME WHEN YOU ARE NOT INTERESTED IN HIRING.