That i based on this study
https://academic.oup.com/aje/article/186/7/824/3848997
The funding is listed under acknowledgements.
I note that only one aspect of diet was looked at namely animal products vs plant based. However over the length of the study other aspects of the diet will have changed significantly by modernization and westernization and possibly the smoking and drinking habits, and it may be that meat eaters are more affluent, and consume more westernized processed foods such as beefburgers. This is not compensated for in their meta study, which is a simple cross correlation only.
Heme iron is a necessary food for human life, as it is far more biovalent (i,e, more easily absorbed) than the iron found in plants. also meat products supply many vitamins and minerals that are essential, and again not easily found in plant foods. Vitamin B12 is one that must be supplemented if following a non animal food diet.
As an aside, Impossible Burger has added a synthetic form of heme iron to their product to make it appeal to omnivores. Unfortunately the amount they add is many times the RDA for us, and apparently 2 burger patties in a meal is starting to become toxic, The problem with this is that it is one mineral that we can overdose on in a fatal way, since excess iron is not excreted by the body, and it builds up quite quickly. The opposite is also a problem in that iron deficiency leads to a form of anemia which can also become fatal. Many on this forum will be taking a heme iron supplement, and this requires the GP to monitor the blood tests regularly to check feretin levels.