People often don't succeed on the GRE due to four main reasons: a lack of clarity on their 'why' for taking the exam, inconsistency in their preparation, using traditional approaches for certain question types that aren't optimal, and failing to develop a comprehensive game plan for success. These factors, rather than innate intelligence, are key determinants of GRE outcomes, as highlighted by Brett Ethridge, founder of ‘Dominate the GRE’.