I know next to nothing about chemistry or biology but I do cook a lot of food, and quite often have leftovers.
After many years in Germany, I got into the habit of leaving food out, and that would mostly be fine. Very rarely would food spoil, at least from a culinary perspective (I'm not disputing the presence of bacteria or harm of its waste).
However after even a few months in Taiwan I learned that this strategy is basically impossible: food left outside spoils within hours.
Given I originally come from a country that is warmer, but much dryer than Taiwan, where food doesn't spoil if left out nearly as fast, I do believe it has to do more with humidity than with temperature.
But yes I'm mostly in a dry environment doing this, I haven't tried it anywhere that was warm and humid at the same time.
It helps a lot to not seal the leftovers but let them have airflow and dry out on the surface. Sealed containers with moisture in them get nasty much faster.
If your immune system becomes suppressed or you become injured, then you're skating on very thin ice.
We've known this for a very long time. There's a reason refrigerators are popular.
And yet, this was common before the electric fridge. I've lived without a fridge for years and the amount of food I ate after being left out overnight would give americans a stroke.
Pork is especially fine if it is properly packaged... That is part of what 'curing meat' is all about.
Most people that brought lunch or dinner to work or school prior to maybe the 1990s thought nothing much of unrefrigerated food being eaten several hours later. Laborers still often do. So do kids.
And tuna at room temperature is surprisingly good (as long as it is not rotten, or the temperature isn't too high). I mean tuna salad, although sushi is served just barely below room temperature.
I remember in grade school taking thermoses of soup for lunch, though I would never do this as an adult (and not only because it was disgustingly lukewarm five hours later).
I wouldn't do it in this weather though.