It worked well because: The state has less incentives to market gambling in a manipulative way - and the profits from gambling were used for charity and treatment of people who gambled too much.

Now thanks to the market, there's gambling everywhere.. commercials, apps etc.

No wonder, the amount of people with gambling addiction in Denmark almost doubled in just 20 years [1].

[1] https://ludomaniforeningen.dk/statistikker-og-tal-om-ludomani/