NAFLD is a symptom of impaired metabolism. The single most effective way to reverse NAFLD is to fix your metabolism, and the fastest way to do that is to eat a ketogenic diet. No carbohydrates, at all.
Going vegan necessities a high amount of carbohydrates, which makes the rapid resolution of your liver fat more challenging.
You can't burn fat when insulin is elevated, and insulin is elevated for hours every time you eat any carbohydrates. You want to enable your body to mobilize the fat in the liver. So you want to maximum amount of time without carbohydrates. Ketogenic eating makes this easy, and you should see measurable results in a few weeks/months.