Gambler
As a scientist by trade, I will not likely rest till I find out what the hell happened that was neither Fraud, bonus abuse, nor a scam.
There are clues, suggestions, lines of possible research, but only the industry knows at present. Previously, the industry has put forward arguments as to why the exact details of a fraud must remain a secret, mainly that it prevents said fraudsters from benefiting from inside information to launch a modified, and far better, attack.
The fact this is also "inventive" and something "not seen before" rules out the traditional forms of bonus abuse, and there are many playing styles that this seems to cover nowdays.
One case does come to mind that may help, and that is affiliate fraud, especially in the case where the casino pays a bounty to an affiliate for getting a new player to register and deposit (irrespective of that player losing or winning). In a few cases, the bounty is greater than the players first deposit, and if player and afiliate were in together, a scam is possible with no bonus, no manipulations etc.
This could even be carried out with a large number of players making relatively small deposits having come through an affiliate link, and then playing nominally and withdrawing without the usual bonus restrictions, this would be incredibly lucrative, but is hardly innovative as it has been tried several times before, with one attempt documented on this forum, bragged about, and not paid. The group affected has now amended it's affiliate scheme to put a stop to it. Under this scenario, a player who deposits, plays a bit, and cashes out the same day, and while this is all going on, is going to be immediately snared by the investigation if their sign-up happened through one of the affiliate portals under investigation.
Bent portals are normally the ones that incessantly spam us, as with the Fortune Lounge issue last year, and at the time the casinos seemed not too concerned with shutting down such portals. Perhaps , if this is part of this issue, they will do more about rogue affiliates if only for their OWN potential protection. Who knows which spammy B*** affiliate will turn to something else if they are allowed to get away with it.