As far as I remember Facebook allowed crypto ads quite some time ago, it's just that they're requiring documents to prove legitimacy of the business.
Also, let's not forget that Facebook doesn't have people that manually approve ads one by one. There are SO MUCH advertisers on Facebook, hence they simply use software to approve/decline the ads. Advertisers could simply not include terms like "crypto", "bitcoin", "blockchain", etc, on their ads, and to simply just label it mostly in the finance category to get past the filter. These ads mostly doesn't take long to get removed though, if enough people report it or if Facebook quickly detected it.
Already reported from my side. I can still see the ad in my newsfeed. I do not know what the reason is hidden behind. Why Facebook system not ban this scam ad?