“You’re talented with magic so let’s make you into a slave”
Sounds like a great idea, why not at least take them in to make the country into a better place.
The below information is based on the original work which this series is expanding on so it may not still be accurate.
The suppression of magic power was done by the king who was using magic to swap bodies with new kids with the monarch's gift. This was done to prevent anyone else from gaining magic power to be able to prevent or stop him from living out his immortal reign. But magic in this world was similar to a programming language/database structure which our MC was familiar with so with the help of his knowledge and now freed slave, he was able to reverse engineer how magic worked and use it for himself. Ultimately preventing the king from stealing his body and partially mind-wiping the king to forget about his plot to steal bodies. Mind you this last bit was literally a single text-only page in chapter 11.