No spoiler tags need for content in this episode or any previous one. Use spoiler tags for anything from later episodes.
Sample Spoiler
If you can see this without revealing a spoiler first, your current app does not support spoiler tags. Browse these comments at your own risk.
Easily the worst episode in the entire show. My partner stopped it half way through and said, this makes no sense. They would send replicas out into space, not humans.
I agree. Charlie fucked up, this is just bad writing.
That ending made no sense? Why would he do that?
My interpretation is David coped with his grief and loneliness by living Cliff’s life. Now that he’s cut off, he’s alone again. Even though there is still Cliff, other than the fact that they had a fallout, David said Cliff doesn’t know what it’s like to be him. The only way for David to not feel alone again is get Cliff to experience losing everything as he did, and to suffer as he does, so he has a companion who he can relate to and understand his pain to spend the next four years with, and they either live through the rest of the mission together or die together. Misery loves company.