What an… interesting promo CW chose to put out. Nothing about the plot, no action, past!Castiel, nothing. Just a snapshot of the cold war between Dean and Cas and poor Sammy stuck in the middle as usual.
Now, if I remember correctly, the last time Dean and Cas had a fight like this complete with silent treatment (and in front of Sam again, to boot) was 8x22. To recap quickly,
Dean tells Cas that he needs him in the crypt and Cas didn’t even acknowledge it before flitting off. He turns up again 8x21, asking for help. Naturally Dean is resentful, and the ‘You didn’t trust me?’ shows how deep Cas had hurt him. Look at it from Dean’s point of view- Cas never seems to trust him- with the tablet, during the entire deal with Crowley fiasco in season 6.
Dean’s whole personality revolves around taking care of the people he loves. He deals with severe abandonment issues- with Sam, with his dad, now with Cas. All of them leaving him behind. Dean has no doubt in his mind that Cas cares, that Cas will do anything for them, but Dean’s never been allowed to reciprocate. Cas simply won’t confide in him till it’s too late.
If Cas had stuck around the bunker, Dean would probably have caved. But he isn’t there (and I’m sure Cas never bothered to explain why he had left the bunker), thereby confirming Dean’s belief that Cas doesn’t need him.
Unfortunately, the angels fall, and when Cas does need him for the very first time, Dean’s forced to kick him out. And he’s clearly torn up with the guilt, considering he apologizes twice for the act, one time when Sam’s getting his head torn open, showing how much he’s been agonizing over it. But it didn’t end there- Dean gets the mark, kicks the shit out of Cas.
Cas says Yes to fucking Lucifer rather than fight along with Dean and Sam. And Dean doesn’t know what to say or feel, because he half feels he hasn’t really been there for Cas, and contrarily, the resentment that Cas doesn’t open up still exists.
After Sam’s rescued in 12x02, Dean lets himself hope again. His mom’s back, Sam’s physically alright, Cas is still there. He makes that elaborate breakfast, hoping he can actually get some time with the family again… Only Cas doesn’t even bother to stay for coffee. And leaves again, refusing Dean’s help quite brusquely.
And now, again. Cas makes a lovely dramatic speech about how much he cares in 12x09. Dean lets himself hope again…
And what I’m guessing is- Cas tries to leave on his own again to fix this. But Dean’s absolutely had it this time and they probably have an argument, Cas wanting to protecting Dean and Sam, Dean chafing at the lack of trust (again). I mean, look at this (gif credit to @codestielckles)-
Sam can’t bear the tension and wants to drown it out. Dean says NO. Dean, the one who tends to avoid difficult conversations by turning up the music. For the first time, Dean wants to talk.. and Cas is not budging. Until he does for Sam. Which leads to this-
Cas will respond to Sam, but not him. Of course he’s pissed.
Poor Sam though, he needs a dog and a vacation after dealing with this shit.