A rapid change in incidence within a genetically stable population implies that nongenetic factors are active and that the influence of genes is relative to population, time, and place. It suggests that something has changed in the environment our children encounter or in the way they are reared.
Not to say this is definitive. Possibly these children died in early infancy before anybody could detect symptoms and describe the disease. But something to think about and look into for people with Type 1 diabetes.