The realpolitik/persuasion/optics angle - Deplorable Pneumonia | Scott Adams' Blog: "Clinton collapsed with some sort of health problem – perhaps pneumonia – at the 9-11 anniversary event. The optics of a potential commander-in-chief collapsing at that holy place, and on an important anniversary, rendered her unelectable in my opinion. I base that prediction on how people will associate her health issues with the need to have a reliable commander-in-chief. Persuasion-wise, that’s a hole you don’t get out of."
And interesting timeline of the most provocative theory here - Complete Timeline of Hillary’s Health