[My bold] That sounds very true. Echoes of @RDP's perfect storm comment, with the notion of a final straw at some point.
The final straw theory is now how I see my ME evolving. I used to think it was "instant" with a flu I never recovered from. Looking back just 3 or 4 years before that particular flu, I noted the stomach bug/food poisoning and EBV of many months duration. My health started to slide with these two earlier instances. One symptom early on was adrenaline surges. GI problems really increased, allergies worsened, developed sensitivity to alcohol, bouts of fatigue etc., etc.