I think there are two primary “whys” that give rise to this behavior; the “material why” and the “teleological why”.
The material why can be answered by the two mechanics at play. The first is because the word “Nigger” is transgressive, no matter what pronunciation is adopted, and the utterance gives Lucas a small rush everytime he says it on social media. The second mechanic is that Lucas has poor impulse control and will simply engage in pleasurable behavior as long as the consequences are not immediate and/or severe.
But why does being transgressive activate that neural reward system in that walnut brain of his? I could shit on a crucifix in front of some Christian clergy and the behavior would certainly be transgressive, but it wouldn’t generate anything pleasurable for me. This is because the transgression needs to have a certain intent, the act itself is just a means to an external end. When it comes to Lucas, acting out with transgressive behavior is goal oriented and serves the greater purpose of eroding boundaries.
Sexual predators like Lucas are fully aware that society views their sexual preoccupations as being wildly inappropriate and that their targets are socially and culturally inculcated against their advances. The systematic weakening of someone’s guidelines for what constitutes acceptable behavior is the primary means by which most sexual predators gain sexual access to their victims.
Almost the entirety of Lucas' social media presence is dedicated to this task. He’ll give you religious arguments for why Gen Z needs to provide him sexual chattel, he’ll give you political arguments, and he’ll give you scientific arguments. Lucas won’t just provide you with justifications for permissibility either, he wants to show you that other people are already gleefully engaging in the taboo behavior and enjoying it, so we get this Bistango fantasy that he manufactured.
Getting a young woman of “Generation Z” comfortable with him saying the word “Nigger” in casual conversation would be an early step in the grooming process. If successful it opens up the possibility to the victim that societal mores might be wrong about other stuff as well. This has a cascading effect that a predator like Lucas would exploit for the entirety of the relationship and if left in place long enough, it will eventually result in the victim totally isolating themselves to be around their abuser.