Earlier quoted context omitted.
You can analyse faces all you want, but whoever the next Prime Minister is, they have a tough job that will probably end with them being walloped in a general election or being toppled by their own party. Boris Johnson is just in an even worse position because he was seen as the leader-in-waiting and he actively campaigned for the policy that made everything so complicated.
And, right now, he has 52% of voters behind him. But, that is somehow making him do a sad face?
And yes I imagine it can't be fun to have to be the one to implement all of this.