First of all, I'm glad your dad made it and is recovering so quickly!
Life is a probabilistic game, and we're all constantly rolling the dice. It's really disconcerting to think of life in terms of probabilities, but that fundamentally is how the world works. My mom, a lifelong nonsmoker, was diagnosed with stage IV lung cancer last year, and this really drove the point home to me. Every cell division comes with a certain probability of a harmful mutation, and cancer happens whenever some cell manages to accumulate enough mutations to blow out cell cycle control entirely, fail to undergo apoptosis in response to cell signals, fool the immune system, direct blood vessels to supply it with oxygen, and spread around the body. It's a really low probability event, but when you have 10^14 cells things can easily go that wrong.
The numbers for stage IV lung cancer are bad: median survival time around 9 months, 5-year survival rate of ~5% (varies by source, but always single-digit). My mom has managed to make it 13 months so far, but it's spread all over her body now despite chemo, so she probably only has a few months left. It's awful, but it comes out to something like a 70-75th percentile outcome among stage IV lung cancer patients.
I don't mean to hijack your thread with my own problems, but I want to say that I know what it's like to have to think about human life in terms of probabilities. The dice rolls are similar with aneurysms, strokes, heart attacks, and myriad other things, not to mention car accidents and other risks we take every day. We all live under a risk of death or incapacitation based on things we don't even know have gone wrong until it's too late.
I find actuarial tables useful in understanding this sort of thing, too. One time, when a student died at the small college I went to (1600 students), I sat down with a table and calculated the expected number of fatalities among a population of 1600 people, split 47%-53% male to female, aged about 20. The expected number of fatalities per year was something like 1.3, with only a ~30% chance of seeing no fatalities in this population in a given year. The fact that we seemed to average about one student death a year made perfect sense in that context.
Losing people is a huge shock, but when I crunch the numbers I'm reminded to be grateful when long periods go by without deaths close to me. So, my congratulations to your dad on his good dice roll and may you, he, and everyone else here continue to roll our dice well!