I think some people are just blessed with great genes and great health/immune system throughout their lives. There are stories of 100+ yos who smoke, who eat typical comfort food everyday, who drink in moderation but consistently etc etc, whose lifestyles are what we basically understand as negative for your health but they are unaffected.
There could actually be a statistical case for people who have genes for longevity who drink, smoke, etc. I don't mean that 'smoking is good for you', but that those who are going to live long, will live long no matter what their personal habits are. Thus when you look at really old people, those that drink / smoke are over-represented. They are statistical outliers of course...
That's overwhelmingly the case. Obviously there are exceptions (which is what the critics will target to try to counter the premise, they'll shoot at the 1% negative case outliers among those with genetics for long life). George Burns is the classic example - 10-15 cigars per day for 70 years, lived to 100. It doesn't make you invulnerable of course, it shifts likelihoods strongly in your favor versus the average person. And you can still do incredibly stupid things to shorten your life, it won't prevent that. If the general public understood how set in barely flexible goo (you can only move it a bit) their health outcomes are at birth, it would encourage even worse diet and exercise behaviors due to an increased belief in futility. If you have the genetics to live to 75, you're not making it to 112 [1] no matter what you do. The news media has a thing they like to do with super old people: ask them what their magic secret is, and the answers are frequently wildly different; that's because it's mostly not what they did, but what they are made of, that produced the outcome (which isn't to say that living a healthier lifestyle, or having some good luck during life, won't help the long-lived get to 106 instead of 97; they too can slightly move the needle around in their box).