There’s a few factors.

First is genetics. Not everyone has the same base level reaction to peppers and/or capsaicin. And it can be either of them causing intestinal rebellion. Some people just don’t respond well to even sweet peppers.

Second is habitation. The more spicy stuff you eat in general, the more your body adapts to it.

But, there’s also variances in mucosa. Our guts, the colon in specific, opportunists produce snot. It’s essentially the same as what coats your throat and sinuses. Not exactly the same, but the same basic ingredients and purpose. Separate from how you respond to the food, and how used to it you are, some people produce more than others.

In your case, I suspect that you have a higher resistance genetically, and produce mucous in your gut that protects you from the irritants that spicy foods have.

If you also have a healthy gut biome going, it’ll add a layer of resistance to things being over stimulated.

And that’s what causes the diarrhea and cramping for most people. The chemicals irritate tissues, so your body treats or like an emergency. That means to increase bowel motility and flush the guts with water. Which means squiiirt.