every promotion carried out by gambling sites has a large enough abuse loophole and it's not just 1 or 2 gambling sites that have experienced this. it's difficult for gambling sites to prevent this, especially those that don't require KYC, the gap for abuse is getting bigger, the problem is that gambling sites that require KYC will be deserted because people prefer non-KYC. the conclusion is that no one is to blame!!
Not that I endorse KYC implementation on any platform, however, only a casino that wants its gambling ground to be overrun with bots would offer large promotions on a non-KYC casino, most of the time, they only offer free spins in those kinds of casinos, which they know they can control, rather than a welcome bonus, which will be heavily abused.
Implementing KYC may limit the usage of bots, but it may also be misused since KYC can be manipulated. We have people who buy other people's information to pass KYC, and they may even pay others to conduct KYC for them if they don't want any company invading their privacy.
Users have got multiple ways for KYC and all other needs. Just think of a below 18 person into gambling. Does he fulfills KYC, no he enters just by accepting he/she is above 18+ and if requested for KYC they night move to another casino or find a solution with someone else details. This happens and Casinos doesn't want their users to move away from them, because the industry is competent and more are on the queue to serve.