The 1-in-1000 low-GPA student who got in wrote a truly unique essay that no other applicant even considered, which is presumably why the university decided to overlook his grades. Not only will choosing a specific topic because it worked for another applicant not give you an advantage (Jonathan Swift gained notoriety for A Modest Proposal but nobody remembers who echoed his suggestions a year later), doing so is the polar opposite of the approach Chicago is looking for.