"We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard. [Address at Rice University, September 12 1962] ". ― John F. Kennedy.
Before I edited my post to keep it more focussed on food processing, I said that vegans, on average, live ten years longer than people who eat meat. I also said vegetarians who are not vegan (who use milk, eggs, and other non-meat foods) "only" live on average five years longer. In general, vegetarians eat a lot more fat than vegans - and in particular animal fat. That could be one factor. Fats tend to store toxins and Animal fats produce biological magnification, where the levels of unhealthy things can get dramatically increased.
But I also said that there almost certainly are other factors, and that Twinkies may be vegan, but they are not healthy.
It appears to be both the degree of processing and the amount of processed food which is eaten that compounds the health problems. And it is much more complex issue, with a lot more variables, than used to be considered. For instance, the topic of maintaining a healthy gut biome wasn't even on the radar until a few years ago.
Vegans/vegetarians aren't simply reducing animal products, they generally tend to eat more whole foods (a lot less processing and more trusted sources), fewer chemicals (more organic), fewer calories, more nutrition, etc.
The etc. goes a long way, and doubtless includes a ton of other lifestyle choices. I bet vegans were less likely to get mRNA vaccines, for example. For example, they are arguably less likely to drive to McDonalds for french fries, and more likely to simply eat a whole potato at home. They are probably more likely to go for a walk than to watch TV. Etc. Etc.
It is not convenient to eat healthy. It is not convenient to exercise. It is not necessarily convenient to avoid unhealthy hobbies. But to the extent these things are made habits, the issues of convenience become less and the difficulty of persisting reduces. Also, a lot of behavior comes down to how you frame it in your mind, your local environment (including social circle) and whether you think long term or only momentary pleasure/convenience.
Actions have consequences. Consequences tend to compound. There shouldn't be much surprise in any of that?