Such people earn money by attracting new players. It's like an affiliate program that pays a certain percentage of the newcomers' deposit. There's nothing surprising about that. People have been attracting others to casinos and other projects using this method for a long time. By the way, the amounts earned using this method are quite large. That's why I see ads for bookmaker sites several times a day on Telegram. It's even become a habit for many.
It is their main job, creating noise, make impressive and attractive content so that they can convince and bring more people to platforms with which they are partnering with in affliate programs. They care about number of new users registered through their referral link as it means more affiliate money for them in future.
About what they shared, is it real, is it efficiently in practice, you only can know it by yourself with your money and bets applied those strategies.