Haha , don't need to be complete vegan , but should be healthy , some people eat pound of grapes at one sitting , and all this fast food ,
this problem is produce by fat and sugar , very important routine exercise , and weight control..
Where I live now , everyone I know exercise every morning ... very healthy City...
Population in USA is about 330Mil , and about 100 mil now is estimate to have some degree of fatty liver and some NASH... this is a very big number ,it is close to 30% .
And probably 10-15 % as you evaluated , in this number are people with full NASH already.
And no treatment so far.