I think that most casinos who operates offline also have online platforms for those who prefers gambling online, but it will be difficult to ascertain the real statistics of bitcoin casinos around the world. Even if a statistic is given, it won't be accurate but i can say that no country beats the United States of America and they are the country that can actually get the right statistics since regulations is tight over there.
am surprised at what i saw, to my greatest surprise, Nigeria being the least among other countries in Africa being listed, when i thought in terms of population and the likes should be the lead, many other underdeveloped countries and having more severe economy problem to have made their citizen found gambling as an alternative to livelihood, because i expected that Nigeria should still leading, which means, in Africa, We are far more better in many aspect.
In terms of gamblers who gambles on bitcoin or crypto casino platforms i can say that Nigeria has the highest rate of gamblers than other African countries but in terms of the number of crypto casinos that operates in Nigeria, i don't think they have many crypto casinos, it's mostly casinos that operates in FIATS.