I kiiiinda refuse to believe this statistic.
Why would it be true when sports gambling is so prevalent? What does polymarket do so well to attract normies to crypto?
Especially for world cup bets the promotions at most bookies are much better than the experience polymarket can offer in terms of UI and UX. So there's very little reason for me to believe that a gambler would go into the trouble to get into crypto just to access polymarket. Gambling requires zero knowledge while crypto required effort to get into.
You are right to question the validity of the statistics, but you are going in the wrong reasoning because that direction is complicated. Why people gamble, who is gambling and how is very diverse in answers and it is going to depend a lot of regions and even the context in which it is happening. You don't mean to say that everyone who will gamble is already gambling, right? So there is always people that are new and being onboarded to gambling in one way another as generations are changing and new people are coming. Polymarket may not be doing anything particularly great, it can simply be hype with a well-designed product that is now trending and if the marketing is done well they can attract a lot of people at this stage. A lot of things got many users in the last decade purely because of hype at the right moment. This is just an example of what could be, it depends really.
The real criticism that is more accurate and is not going to depend is on how they are claiming that someone is a first-time crypto user. The data that they have does not show them that at all. If I joined it with a new wallet or simply a fresh address during the time they were collecting this data, they probably would also have considered me a first-time crypto user and it could not be farther from the truth. The issue really is about the use of statistics, and then manipulating the gathered data for a marketing stunt that makes a false claim.