The season 5 finale of The Expanse abruptly kills Alex's character off, but this death is the best course of action the show's writers could take. The episode, entitled "Nemesis Games," is packed with plot developments--one of the most striking being when Alex Kamal (Cas Anvar) suffers a fatal stroke while trying to save Naomi from the Chetzemoka. This all happens very suddenly; he stops responding to transmissions and the show cuts back to Alex within the ship. Blood drips from his nose and he offers up eerily serene last words: "That was one hell of a ride." It's only later that the cause of his demise is revealed: an apparent stroke from prolonged high-g exposure without proper protection from a special adrenaline-blood thinner-amphetamine concoction, which is specifically designed for preventing strokes and aneurysms during intense space travel.
But, just as The Expanse has taken pieces of book characters and applied them to different ones on the show before (Camina Drummer is a prime example of this), the writers have done the same with Alex's cause of death. In the sixth book of the eponymous series, Fred Johnson is actually the character who dies of a high-g induced stroke. Given this information and the abruptness of how the death was executed on-screen, it's impossible to dismiss the likely connection between Alex's TV demise and the recent string of sexual misconduct allegations that have arisen against actor Cas Anvar. The accusations, which were brought forward by multiple women this past June, allege that he harassed and/or assaulted them after they met at fan conventions.
The series' showrunner has said that there were some behind-the-scenes thoughts about The Expanse possibly killing off a character early in season 5. So, was this the writers' plan all along? Though this was at the end of the season, was TV Alex already set to die? It can't be said for sure; however, this specific way of making Alex's character expire from the show is the best course of action given the circumstances. By using Fred Johnson's death from the books, the show still mostly follows the source material, while taking typical Hollywood creative liberties. With the profound impact that the #MeToo movement and similar societal social reforms have had in recent years, it's in the show's best interest that Anvar gets the boot.
Plus, this death isn't anything that departs too radically from the narrative. It fits the tone of the episode, one densely packed with slow-burn action. Both Alex and Serge meet untimely demises, it's discovered that Marco Inaros has taken control of the Ring, Michio Pa gets some brief time in the limelight, the Expanse season 5 ending scene depicts a mysterious Martian ship-destroying entity, and more. A lot happens and it all follows a coherent theme of grave seriousness, loss, and taking necessary action. There isn't much room for anything too chaotic or source material-divergent, and a simple death explained after the fact is a tad odd, but mostly blends in with the rest of the plot.
As it's said in the episode, the possibility of that kind of space death is a risk all the characters regularly take. Alex's demise is simply another transferred character event. Similarly, Fred Johnson doesn't die in what happens at Tycho Station within the books; he takes on a death that's unique to the show. So to write an on-screen version where Alex's character also meets a death that's solely for TV fits right within the show's creative parameters and doesn't create problems heading into The Expanse season 6. Despite whether or not Alex's death was contrived by The Expanse writers purely as a judiciously weighed response to controversy, it was the best it could be.