G2A made an offer years ago to any video game devs that they would compensate any devs if they and an external investigation could prove that the keys were illegitimate.

Wube the company behind Factorio was the only one that took them up on the offer and they were right, the keys were illegitimate.

https://www.gamesindustry.biz/g2a-and-wube-software-settle-usd40-000-chargeback-dispute

https://www.pcgamer.com/g2a-has-paid-factorio-studio-nearly-dollar40000-over-sale-of-illegitimate-keys/

Official announcement from G2A: https://www.g2a.co/g2a-strikes-anti-fraud-agreement-with-indie-developer-wube-software/

About the issue from Wube: https://www.factorio.com/blog/post/fff-303

Follow up [last section]: https://www.factorio.com/blog/post/fff-348