Some of us have legacy status, being the sons, grandsons and great grandsons of Harvard graduates. If we meet the minimum grade requirements we get in, and if we manage to pass enough courses we earn degrees.
Certainly some Harvard grads are smarter than others. That goes without saying. My sister and I both have graduate degrees in history, but she is frankly a genius and I (comparatively) a mere plodder. Obama and Bush both went to Ivy League schools, but Obama was a star who edited the law review and Bush scraped through on his legacy status.
In fairness, however, all graduates of every university have proven their ability to work through the system and learn their subject well enough to convince the experts that they deserve a degree. Hiram Ulysses Grant was not top of his class at anything when he graduated from West Point, but the work ethic and determination he demonstrated there were obviously not wasted.