Watching his videos, what I find really disturbing in hindsight is his fundamental misunderstanding of how the science of cooking works. Most cooks don't know "food science" but they get a general sense of what works from experience and common sense, but Jack totally lacks that. Things like undercooking meat, not understanding how bacteria grows, not understanding how flavors are meant to compliment or contrast, or how some things just don't go together, and even the little things like making "pineapple jello" with actual pineapples and lemon jello; pineapple is really acidic, so the jello won't set. (Some canned brands aren't acidic enough to break it down but he never even mentions that and the jello always looks very watery so nvm). Not understanding how quickly calories, sodium and other bad stuff can quickly pile up when you recklessly mix things together, etc.
All of it paints a portrait of someone who just simply doesn't understand how food works, and just throws stuff together haphazardly rather than actually cooks. I'm not surprised he gave himself multiple strokes chugging 12 energy drinks a day, he probably didn't even think for a second about potentially overdosing on caffeine.
His understanding of food science is on par with a 16th century plague doctor's understand of medical science, and the results are just as disastrous.