How you react to eating unsafe food can depend as much on you as it does on the food. What you could eat without noticing any issue might make some other person very sick and kill yet another person. It can depend on factors like how good your immune system is feeling that day, what it has experience dealing with, how good your overall health is, and what specific species makes up your gut biome. Or, counter-intuitively, sometimes if you are less healthy overall, it can mean that something doesn’t affect you as much, eg if you have gut issues that prevent you from absorbing toxins related to some pathogen, you could pass it fine while it knocks a healthier friend of yours on their ass.

For the mayo, my guess would be the ones usually not kept in a fridge likely use more preservatives, though I’d bet they also have a shorter shelf-life than the ketchup and mustard pumps. Another possibility is that it isn’t really mayo but just something that looks and tastes like it but was made very differently.

For which bacteria is present on foods, I believe that this is very region-dependent and that the supply chain will play a bigger role than the food type (though food type will affect which bacteria and fungus species thrive on it). Might see different microbe profiles based on time of year and all of them will be evolving new clades and going extinct over time. Not sure how much of an impact survival of the fittest has on what this actually looks like from year to year or decade to decade, but understanding what microbes are doing what to your food could be a moving target similar to trying to keep track of what covid clades are associated with what symptoms or traits.