Blight diseases are always most troublesome in cool, wet summers. Sanitation is very important. Immediately get rid of all the dead vines and fruit. The fungus can live in decayed plant refuse in the soil. Do not compost infected plants.
Planning is the next step.
You were right to move or rotate the crop. See to it that next year your tomatoes get planted where no tomatoes, potatoes, eggplant or other related crops have been grown for at least two years. Keep your garden well-weeded. Nightshade, which is a weed in the Solanum family just as tomatoes and potatoes are, and other weeds can carry the disease and spoil your rotation scheme. Next summer space the transplants far enough from each other so that they can get good ventilation.