I don't think it's even possible to cover every sport. Nevertheless, as this project gets bigger, it'll probably attract more attention and smaller sports can try broker a deal with them in order to get their game more popular. It's a matter of quality over quantity.
I don't understand how bets can make smaller sports significantly more popular.
It's natural for the people to get attracted to something big like a successful and diverse project. If a person, say, bets on his favorite soccer team, through ads he can get familiar with other sports and so on.
I think that those sports for which more bets are made automatically can become more popular, everything is interconnected