I don't know where you're from - but I'd be genuinely surprised if that data were true. It's hard to believe that any country's primary source of revenue is the gambling industry, when there are likely other, larger sources of revenue, such as natural resources or taxes. I know the money flow in the gambling industry is very high - but I don't believe that the taxes from it can outweigh other sources of revenue for one country.

Some countries may still have the largest source of tax revenue - but that's from all applicable tax targets, including the gambling industry and other physical industry. It's hard to believe that this data is accurate - unless your country has no other sources of revenue.