Splunk Frontend Engineer interview questions

I applied and immediately received a link to a homework assignment without talking to a recruiter. It said I had seven days to complete it. I didn't have time during my work week; it was the 4th of July weekend, so I just ignored it. Then, about three weeks later, I got an email from a recruiter asking if I was still interested. I replied yes, got a new link, and did the assignment, not once speaking to the recruiter. Expectedly I received a generic rejection with no feedback.

Interview was 2 phone rounds and a final 5 hour on-site interview. Splunk didnt waste any time and it was all in around 2 weeks organized well. But the worst part was their communication after. I was told that I have the offer from HR after which there was no communication for one week. After persistent calling, the HR said the position was put on hold. I dont understand why Splunk should waste so much of my time and their time over 2-3 weeks and give me the offer and then say no position. This is not very professional on their side on how they treat interested applicants.