It's pretty simple: he did made ML work before almost anybody else did, and kept working on during the deep network explosion, and is now running Facebook AI, which has to deal with these sorts of problems with practical solutions on a daily basis, with billions of users. That sort of daily experience counts so much that I would I would place him in the "knows 100X about every area of ML" (excluding rare subfields).

It's rare but I have encountered people outside my field who knew more than I did about my field, because of their daily experiences over decades, or their raw intelligence. Yann seems to have both.