Many people cured their autoimmune diseases with a larger dietary change. If diet heals the autoimmune disease how can one say that it's the body attacking its

Many people cured their autoimmune diseases with a larger dietary change. If diet heals the autoimmune disease how can one say that it's the body attacking itself "just because"? This clearly shows that food is (for at least some people) the primary cause of "autoimmunity".