@cholash Yes, after I posted it I thought that too. NTM is in water, soil, and in the air we breathe. I agree, the predisposition, is the million dollar question.
Are there studies that demonstrate that certain other factors such as Gerd, Asthma, other lung disorders, COPD, maybe smoking etc make it somehow more likely to get infected with NTMs.

Do the structure / damage in the lungs and presence of earlier specific infections play a role? So many questions.