BlackRock Software Engineer Associate interview questions

Applied online and received a HackerRank link. There were 3 questions. One algorithm based, one REST API implementation and one DB query. Cleared the HackerRank step and received response from the recruiter with a questionnaire that there will be a onsite interview (virtual). I responded to the recruiter and sent a couple of follow-up emails, but didn't receive any response. GHOSTED by the recruiter. Unprofessional and waste of time.

I had applied on BlackRock career website, the HR contacted and scheduled a telephonic round. After that, a F2F round was scheduled. The rounds were very interesting, there were core java questions, few puzzles. They would dive really deep in topics and codes. Finally, the HR contacted for the offer, I sent documents needed for the same. After that nothing!!! I don't know how long it takes to send offer letter but it would be nice if the HR could at least reply to the follow-up mails I am sending almost every day. Considering that BlackRock is tagged as an "engaged employer", it would be great if you improve communication protocol with selected candidates. This mystery/suspense does not help anyone.