Citizens Development Business Finance interview questions

I recently went through the interview process for a Executive trainee in Data Science position at the company. The overall interview experience itself was positive — the interviewers, including the director, were friendly, encouraging, and created a comfortable environment to discuss my skills and experience. The process involved three stages, including technical questions, an assignment, and a general discussion at the end with the director. The director even discussed what teams I could be assigned to and also welcomed me to the company after I mentioned that I could join immediately. However, I was disappointed with the lack of communication after the final stages. One week later the HR called to ask my salary expectation and I told them the same amount they had kept aside for this role. Despite being told that I would receive an update, I did not hear back from the HR team. After 3 to 4 weeks I took around 3 to 4 calls and none of them were answered. After the 7th week I tried a hotline number and I was tranferred to the HR department where I was told that the vacancy was filled. My problem isn't the fact that I didn't get the job but the fact that I was welcomed to the company and talked to as if I would definitely get the position and and yet wasn't given any assurance about it afterwards. They didn't even contact me through a simple mail to tell me that I wasn't selected, which is basic courtesy. I don't know if it's because of the lack of communication internally or because the HR can't do their job properly or BOTH. Overall, the interview experience was pleasant, but better transparency and follow-up would have made a huge difference. Hoping that no one else has to go through such an experience in such difficult times.