Because it’s showing the galaxy celebrating the destruction of the death star.
Which is stupid if you consider the Empire giving up the ghost just 'cause Palps is gone a stupid idea.
The only thing stupid here is to assume that the Empire has given up. Showing spontaneous celebrations/uprisings when people heard Emperor was dead do not indicate in any way that Empire has given up. Killing Emperor and his successor in a system where all the power is concentrated in one man would certainly cause enough confusion for such uprisings to be possible (at least until they crack them down). It is not the first uprising in history that has been eventually cracked down.