1. Support from the government.
Countries who gamble a lot has solid laws protecting their players so gamblers in those countries can just freely gamble as much as they want without having to worry about their rights. This doesn't mean that the countries have very free and loose rules but it just means that they have clear frameworks. Some other countries have some limitations but since their rules are clear, many still gamble.
2. Bigger paychecks.
Not all rich people are gamblers but they certainly have more chances to gamble if they wanted to. According to data, the higher the income is in some countries the more people gamble in that country. Since the average citizen is earning a lot, even if they spend quite a significant amount of money in gambling this will still not cause financial doom.
Is it fair to assume that a better economy and a solid framework will make people gamble more but be addicted less?
A better economy definitely has a very important role it plays in the lifes of people in a country which may include people who gamble as well. But when it comes to gambling and getting addicted, a good economy is no fault at all and shouldn't even be mentioned, people are solely responsible for how they choose to go about their gambling activities, a good economy will not immune people in a country from getting addicted to gambling if they choose to gamble recklessly.
But it is indeed true that in a country where money can be easily earned, there is the likely hood of interested parties getting involved in gambling so long as it's not an activity that is banned by the government of that country, but then, proper moderation must be applied because anybody can get addicted and may not even know when it happened.