I think these influencers must know their target audience before accepting the offer or should not be included in their blogs or videos?
they just don't care about it, because the most important thing for them is how they can make money from the promotion. they don't care who their audience is and who they get the money from or what brand they promote, the important thing is that they can get money and that's enough for them.
if we say they don't care about this, that's not true, but it's just that most of these influencers are stupid, so they don't know what they are doing, promoting something that is very vulnerable to children.
I think it is hard for them target specific audience because the video posted can still go viral or be shown on someone else feed even though they don't have interest with it. The only thing that they can do, is to choose properly if what they promote is legit and also the influencer should not be misleading on promoting it. Unfortunately many influencers nowadays are not like this but they are like what you describe there.
It's not that they are stupid to not know what they are doing but they are wise and selfish. I think children are still hooked in video games and not in gambling but many adults now are addicted to it, based on the comments I read online.