You are right. For now I think only Telegram and X give the freedom to promote something that is 18+ or something that is considered illegal in some countries and legal in others. I don't think BetHog should try to create Instagram or Facebook if they don't give permission for BetHog site advertising. And actually we can see some other platforms that are successful just by using Telegram and X. As @Alphakilo said, a platform needs a promotion and marketing team that can create good promotional content for certain events.
They must assess their resources before creating new accounts on other social media because even they don't spend money for advertisements there, they will have to spend human resources to handle those social media accounts.
It does not help anything by creating accounts and let them unlively with no posts and activities but it has risk of account hacks that can be used to spread phishing links for example. If happens, it damages the business reputation and harm users.
I agree that X is a perfect place for advertisement from cryptocurrency to gambling, Telegram is a good messenger with good privacy and open space for advertisement.