Worldwide recognition
The first and most important factor is worldwide recognition and participation in the sport. While there is not a set quota of participating countries or worldwide competitors that would automatically qualify a sport as being Olympic quality. However, since the admission process includes a vote from the National Olympic Committees, it is important for the sport to be widely practiced and recognized in the largest number of countries. For example, it wouldn't make sense for the NOCs to vote for a sport in which only a handful of countries would participate.
International governing body
Each sport in the Olympics is governed by an independent federation. Before being accepted into the Games, the sport must have an organization that oversees a large percentage of the sport's activities worldwide. It must also be capable of stepping in and overseeing the sport's Olympic events. Karate, which is not currently an Olympic event but has been nominated several times, would be directed by the World Karate Federation if it were to pass the IOC vote.
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This is why Esports will never become an Olympic sport.