Suppose billiards made it into the Olympics, would there be enough pool fans interested in participating to attend and support the Olympics in the host city.
The worst decision IOC can make is to gamble on a sport, and attendance/viewership/interest is not as high as it was promoted. IOC wasted their time and has two wait the four years for another chance.
If billiards debuted in the Olympics it has to have enough support to keep it there. There has been a lot of interest in why billiards/snookers is a great candidate. But which events show the numbers, or fans willing to travel to watch those events live and in person.
The best I usually see are fans show up around the finals of a major tournament, but throughout the earlier matches are not available.