Why you are assuming that they won't last long in youtube? Are you expecting that youtube is going to do the same as twitch did? No I don't think so because I've seen different contents in youtube and some can even be called inappropriate but they haven't been removed up until now.

Other than youtube, there are other streaming sites out there which are not strict as twitch. They can always use that. They can also create their own streaming platform as you suggested. It will never be a problem for them since they have a lot of money. They can hire a good website developer and then run some promotions. Pretty sure that many top gambling sites or those who got removed from twitch are going to migrate there.