Devexperts Software Engineer interview questions

The overall process was great, everything ran pretty smoothly and fast, the HR was extremely responsive and provided immediate feedback after each round. Overall there were 4 steps: 1) HR call 2) On-line test 3) Tech interview 4) Cultural fit interview The tech interview was not very difficult, as I had knowledge in a relevant field, the cultural fit interview was also fine. Afterward, they made me an offer 20 percent less than the minimum amount we negotiated in our first interview with HR. I ended up just taking a long time. Why was it not possible to discuss this at the start? In none of the interviews, I was not told a word about the overestimated (although this is not the case) salary expectations.