Wierd Glitch?

Yep, definetly, the bomb exploded while you where over the blast zone

The Up-Trow animation of Kirby and Meta Knight (and some others i thing) works different, during the animation, if you get over the blast zone, you won't die, but since the bomb exploded, it interrumped the animation and both died.

This could work as suicidal shenanigan for doubles battles, seems really cool to exploit

What they said.

i think what happened was the bomb exploded when you was outside the blast zone, knocking both of you out of the throw (the only thing keeping you from dying)

Maybe the crash bomber exploded right when meta knight was at the ceiling of the stage, and it would've hit both of you upward the tiny bit to reach the deathbox above the ceiling