Is the first bit of your post a genuine question? I can't quite work out if you just don't understand the words or if you're being rhetorical.
Anyway, I'm sure he is angry and disappointed. The point is, he just won't be as disappointed as a manager who expects to be here next season. I'm sure in your personal life you are unrelenting in your work and would never ever let your attitude be affected by such things as future employment prospects. But unfortunately the rest of the world is not like that, and it makes a big difference to how you behave.
[Cue the response: yeah but yeah but he gets paid £6million, to which I will preemptively respond: salary size is a level effect that doesn't make a difference to the point at hand. If anything, being paid that much is actually more likely to him care less.]
I`m being rhetorical.
Smirking does not convey angry or disappointed, it portrays petulance, arrogance and not giving a shiz.
It`s what my 12 yr old lad does, when he`s been caught doing something and is trying to buy himself a few seconds to think up a convincing lie.
Irrelevant of what my personal thoughts are on him, he represents our club, smirking after getting gubbed, does not reflect well on the club and only serves to disengage himself further from a fan base, that we saw turn properly on him for the first time today. ( expect it to get much worse )
As a pundit, he will have had proper media training on the the does and dont`s when on camera. He`s also done hundreds of interviews too. Smirking when trying to convey disappointment is probably not part of that training.
He`s not just an un likeable manager, he`s an unlikable human being.
He`s a stain on the club mate, yet you and and a couple others just don`t seem to be able to get your head around it.