Sometimes admission officials work in mysterious ways. The admission committee at Case may have decided that, despite your strong grades and test scores, you hadn’t given any indication that you were truly interested in enrolling, or perhaps you were sloppy with deadlines.
Another thought is that you may require a lot of financial aid. Even if you are a strong applicant, if your financial need is very high, the college officials might have decided to put you on the waitlist until they see how much money is left in their budget after making financial aid offers to more desirable candidates. Some colleges that are “need-sensitive,” as Case is, can decide to take two decent but not stellar applicants who don’t require a lot of aid rather than one somewhat stronger student who does. So sometimes when an applicant is waitlisted or denied and sees that a weaker classmate has been accepted, it could be that money is at the root of the decision. If you are an international student (not a U.S. citizen) and you applied for financial aid, then money is very likely to be behind your Case outcome. Most colleges set the admissions bar far higher for international applicants who need aid than they do for U.S. citizens and permanent residents (who qualify for U.S. Federal funds).