Death Stranding EXPLAINED: All Ending Questions Answered
2. Amelie's Change Of Heart
This is where Higgs comes in. Though he was initially a porter working with Fragile, he was seduced by Amelie, who gave him DOOMs and the power over the Beaches and BTs (via the creepy doll that acted as a physical connection to Amelie's Beach), manipulating Sam into thinking he had his sister hostage.
She counted on him coming to save her, but she didn't count on him, and the likes of Die-Hardman, Deadman, Mama and others, becoming so committed to the cause of rebuilding America and finding genuine connections along the way.
Consequently, she offers Sam a choice: join her for the final moments of existence and end the suffering, or let the Death Stranding extinction event play out over the course of thousands of years, with the inevitable demise she trigged doomed to eventually happen.
Putting his weapon down, Sam hugs her, and after commenting on the resilience of the human spirit to persevere and come together in spite of how bad things got, she agrees to stay on her Beach alone, and sacrifice the connections she'd made in order to postpone the extinction as long as possible.
It's a tragic fate, and she doesn't initially know why Sam would want to live in a world doomed to die, as existence in general is nothing more than a fluke in her eyes, and Death Strandings will keep happening to 'fix' it.
Of course, the reason is that in real life everyone knows they're going to die eventually, and it's about what you do in the time you have available, and the relationships you forge along the way, that defines the human experience and makes life worth living in the face of death.
Sam is pulled from Amelie's beach by the rest of his team, who locate him because he still has Die-Hardman's revolver. He leaves forever, as Amelie sees five figures - the same five figures from Death Stranding's first trailer - in the sky away from the shore: the five other Extinction Entities who came before her.