The problem with Sam caring for Nick is not that he’s caring for Nick – that’s entirely in character for Sam – or even necessarily that Mary doesn’t fully understand why that has to be hard for him – because nobody ever fully told her – but it’s that the writers, once again, gave everyone else an opportunity to talk about their Lucifer related trauma but Sam.
I don’t blame Mary or Jack for not fully knowing, because how could they (Castiel is another bag of issues here), but we just sat through two consecutive episodes in which everyone but Sam was allowed to textually acknowledge how difficult it can be to see the face of someone who’s responsible for much of your trauma. I’m tired.
By accepting Sam’s declaration that there would be no new King of Hell and by not challenging it, the demons acknowledged his authority. Sam may not be the king of Hell in name, but the hand-selected followers of the most recent contender to the throne literally would not dare to face him and fight for it.
“i have to think about the good, sam, because if i don’t, i will drown in the bad.”
— mary winchester, mirroring her son from over ten years later in 2.13 (there’s so much evil out there in the world, dean, i feel like i could drown in it)