Answer
John Connally passed away due to complications related to pulmonary fibrosis, a chronic and progressive lung disease characterized by the scarring and thickening of lung tissue. This condition impairs the lungs' ability to exchange oxygen and carbon dioxide, leading to shortness of breath, coughing, and fatigue. Despite advancements in medical treatment, pulmonary fibrosis can be a life-limiting condition, as was the case for John Connally.