Atos Off Campus interview questions

They carried out Group discussions, aptitude test, technical interview and final HR interview. Finally they told me that I was selected and will get my offer letter within 2-3 days. Its more than 2 months now and I haven't received any offer letter yet. They shortlisted more than 300 students in final HR interview and only 20+ students received the offer letter, few of them also got the rejection letters, and few people like me haven't even received a single response. When contacted to the HR team they told that the criteria was suddenly revised. Then the question is, why the ATOS people arranged the big off campus and shortlisted so many people when they were not this big requirement?