It's correlative. TMAO tends to be above normal levels in people with advanced athersclerosis. TMAO is a protection mechanism for a protection mechanism (uric acid).
Heart disease is the result of damaged carbohydrate metabolism, and always will be. Which explains why the vegan group was fine, but the other group(SAD diet full of PUFA in cells) was not.
So, keep eating your red meat and try not to take mainstream science so literally because it's always mostly wrong(think seed oils being "heart healthy")
He who dares not offend cannot be honest.