The 20th-century ulcer epidemic was a sign of good health in American people - good diet, strong acidity and healthy immune response actually make ulcers more likely. That's why businessmen eating giant T-bone steaks were prone to ulcers.
Peptic ulcers became more common in the 20th century at the same time that these theories of Freud and other psychoanalysts became popular. And somehow those meshed, and this tradition emerged that ulcers were caused by stress or turmoil in one's life.
To gastroenterologists, the concept of a germ causing ulcers was like saying that the Earth is flat.