Coforge Technical Lead interview questions

I had a total of 5 rounds: 2 virtual rounds from Coforge, followed by 1 client technical round, then another client techno-managerial round. Later, they asked me to attend a final in-person face-to-face technical interview. They made me write on a whiteboard and subjected me to deep grilling again. After thorough follow-ups with the HR, he concluded that they didn't find my profile convincing. Why so much harassment? You could have just said that after the first round. Why take 5 rounds and then, even while I was writing on the whiteboard in front of them, the client claimed I was using AI? What kind of way is this to say no?