Of course, this death isn’t mean to last forever, considering Brainiac will still be a major part of Krypton Season 2 in future episodes.
Seriously, Brainiac even said, “Come now, you didn’t really think it would be that easy, did you?”
You gotta give it to the show for setting up exposition for how Brainiac could “survive” a death, so to speak, minutes before killing off that iteration of the comic baddie.