A specific reason is not a logical reason; sure, the decision ‘made sense’ to that person at the time, but it’s irrational within the broader schema of life.
It might be "irrational" in some sense with unbounded knowledge, but we only have bounded knowledge. I'm not sure using the former as a definition of "rationality" is useful. Rationality should be a sort of preferential ordering of choices according to one's bounded knowledge.