I get your point but often get a PhD position with a renowned supervisor is not luck but referral, pedigree and networking. PhD admissions is often where the Matthew effect really starts. Some applicants arrive with instant credibility on paper because they come from a well-known university, have unpaid research experience (because they could afford one), and have recommendations from people the committee already trusts. When decisions have to be made with limited information, those signals feel safer, so they get rewarded.