> a weaker immune system or microbiome is plausible > Think of it this way: ... OP already said it's plausible. Your image doesn't add to the evidence at all.

> a weaker immune system or microbiome is plausible > Think of it this way: ... OP already said it's plausible. Your image doesn't add to the evidence at all. The truth is, we have no idea about immune and gene regulation. A lot of the simplistic understanding you learn in school is falsely making people believe the body is a "machine" we can control or even comprehend. Medicine doesn't know shit. All we have, are some correlations with an increase in autoimmune disease, allergies and lymphoma, and increasing hygiene. Could also be microplastics or hormone disruptors, social isolation, stress, overweight, lack of sunlight, climate change... . The immune system is insanely complex and a huge bag of innovation and legacy making many functions redundant and incredibly hard to decipher. And some "healthy exposure" to pathogens really is a coin toss, as it may not be the contact, but surviving the sickness you benefit from. So a severe fever may slightly decrease your cancer risk, but comes at the risk of dying from, well, severe fever.