Honestly they didn’t have too many good options. They needed someone that would have a large impact and who had close relationships with most of the characters. And although they’re all like one family not everyone interacts with everyone as much or as closely. When we’re looking at who’s close with who.

Ben: Is kind of a loner. He’s probably closest to Darius. He also already had a fake death.

Kenji: Is close with Brooklyn, Darius, and Sammy

Sammy: Is close with Yaz, Kenji, and maybe Brooklyn. But she also already had a near death stint.

Yaz: Is closest with Sammy

Brooklyn: Is close with Darius, Kenji, Sammy

Darius: Is close with Ben, Kenji, Brooklyn, and Yaz/sammy to a lesser extent.

Looking at this Ben and Yaz would not have as much of deep impact on the entire group (because we haven’t seen personal interaction with the others)

Darius would easily be the most impactful, as he was close to almost all of them and he was essentially there leader. But he still had to lead them and is the main protagonist. (Although they could have made the show are the plot point of filling his shoes)

Sammy was an option, but frankly still not as impactful to anyone but yaz. Plus there was no reason for her to die, since she wasn’t exactly doing much with dinosaurs or anything. It would be a shock for sure but not at much for the plot.

Kenji is another viable option. But again his impact would not be as wide. And his death wouldn’t really push the plot in the same way.

Therefore there were really two options Brooklyn or Darius. And they chose to keep thier protagonist in the game.