suru verb (special)
prove fortunate; turn out well; work out favorably
Used when a situation or condition ends up being advantageous or lucky, often with a nuance of 'fortunately' or 'luckily'. Commonly appears in the pattern ～が幸いする or ～が幸いして.
雨が幸いして、人出が少なかった。
The rain turned out to be a blessing, and there weren't many people out.
彼の経験が幸いして、
His experience proved fortunate, and the problem was solved quickly.