Why the hell would they drop it from the sky? They had a hunter that could create gates within the enemy castle. I'm pretty sure being 10m or 50m away from ground zero of that explosion would not change its effect.

The only excuse that would make sense is that Netero was confident he would be able to kill the King with Zero. Still, it is dumb strategy. Risking your Queen when you could have checkmated with a couple of pawns is foolish.

The entire bomb reveal is cheap to be honest. It came from nowhere.