The Vocal Synthesis channel on YouTube trains text-to-speech models using publicly available celebrity voices. Then using this new computer-generated voice, the celebrities “recite” various scripts. For example, the above is Jay-Z rapping the “To be, or not to be” soliloquy from Hamlet, but it’s not him.
Find out more about the voice generation here, which was developed in 2017. Maybe more interesting, Jay-Z recently filed a copyright claim against the videos.