when you say of all people, you are emphasizing that sb is the person you would most or least expect to do sth; used to express surprise because sb / sth seems the least likely person, example, etc.
Oxford70% of films
when you say of all people, you are emphasizing that sb is the person you would most or least expect to do sth
Oxford30% of films
used to express surprise because sb / sth seems the least likely person, example, etc.
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition