It's the body's response, your immune system, how you take care of yourself sick are all factors. This doctor probably ignored his symptoms and popped Tamiflu and ibuprofen, maybe a narcotic for the cough (guessing), unknowingly developed double pneumonia (can happen fast), went to his car for a nap and never made it out.
Some are saying this flu, H3n2, is attacking the heart muscle in some people, but I've just heard this, not read it anywhere.
There is also a thing where people with very good immune systems die suddenly from influenza: the immune system has a kind of storm and goes haywire. Like the 1918 flu was one of those strains. It's scary this year, glad you guys are OK.