Here's why:
* Exploder's effect is a destruction effect: It destroys monsters on the field.
* Destruction effects don't trigger replays: Replays are typically triggered by cards that change the outcome of a Duel, like "Time Wizard" or "Cybernetic Fusion Support".
Therefore, even if Exploder destroys all monsters on the field, the Duel will continue as normal, with players able to summon new monsters or use other cards.