How can we reconcile the fact that sins prevent memorization and success with the existence of non-Muslim or disobedient Muslim doctors and scholars who possess a high ability to memorize and succeed in their fields?

Sins darken the heart and extinguish the light of the intellect, depriving the servant of divine guidance and success. They lead to one another until the person is no longer guided to obedience, as Allah Almighty says: "So when they deviated, Allah caused their hearts to deviate," and He says: "And We will turn their hearts and their eyes away as they did not believe in it the first time." As for the strong memory of disbelievers and the breadth of their knowledge, it will not benefit them in the Hereafter. Allah condemned them for being intelligent in worldly matters but not in matters of religion. Their knowledge does not extend beyond the apparent aspects of this world, and they do not distinguish between knowledge and ignorance, because their knowledge did not lead them to know Allah. The sum of this is that sins stand between the servant and divine success, so he does not know what benefits him nor is he aided in preserving it. Allah's giving to sinners and enabling them to achieve their aims might be a gradual enticement (istidraj) for them, so He seizes them suddenly while they are heedless, as in the Hadith: "If you see Allah giving a servant what he loves of this world despite his sins, it is but a gradual enticement (istidraj)." Then he recited: "So when they forgot that by which they had been reminded, We opened to them the gates of every [good] thing until, when they rejoiced in what they had been given, We seized them suddenly, and they were in despair."