Launching an event, as you said, can be very effective in attracting people to visit the site, especially with the lure of giving prizes to people who manage to find bugs or win a game. That is a great way of promotion. Moreover, they can provide additional bonuses for people who send some money to play gambling there.

Maybe they can also invite people personally as beta testers to test their site, look for security holes that are still leaking, or look for bugs on their site. There are many ways to grow their site, depending on the site team and their plan.