Well, I thought about repeated explosions as well...But I think the final big explosion has much more of a shocking effect, think of it like the core exploding.
Many smaller explosions might also strain the server a bit more...
Hm...maybe the first explosion could even be like an "anti-shield" explosion, which occurs once the ship's hull is at 0, and then the final one happens when the ship finally "disappears".
GBs also take some time to explode, right?
I think transports should act that way as well...