that’s what we call a character developing feelings

See, no, that’s not it. That’s what someone who hasn’t seen Supernatural would think when looking at these gifs. What they lack is context. Cas has always had feelings for Dean and about Dean in varying degrees. Hell, the reason he is the way he is in the first gif is because he had too many feelings about Dean after Sam’s fall, and he chose to put aside his own feelings for the good of Heaven and to keep Dean safe. He’s still trying to keep Dean safe, and the best way he can think to do that is not to get the Winchesters involved and throw himself into the war to end it quickly. He can’t permit himself the luxury of stopping by Dean’s bedside to talk about feelings or responding to every “hey Cas, what’s up?” call. Which is ironic, because maybe if he had stopped by to explain things, he wouldn’t have that Pyrrhic victory in the second gif - he’s close to winning the war, but he’s lost Dean’s trust and wellbeing, the very things he wanted to keep safe. The second gif isn’t about developing feelings, it’s about showing feelings, and realizing too late that trust has to be reciprocal.