I don't know why
Why is Hikaru so emotional in Champions Chess Tour?

Just having an off form few days at a bad time. That'd make anybody upset. Maybe he feels extra pressure because of the Kramnik business too. Everyone has bad runs and he's on one now.

he's really wearing his emotions on his sleeve
He's been that way his whole life.
not like that though... at least since he started streaming

Perhaps he's been playing too much blitz against lower opponents - got too comfortable playing "fast and loose" and getting away with it.
Hikaru is, of course, no stranger to elite competition. But there must be some sort of impact on your game if you're continually playing against weaker players ...
I know he's struggling, but he's really wearing his emotions on his sleeve lol