If the electromgnetic build up wasn’t released, the ‘cork’ that was at the source of the island would have become dislodged, destroying the island. Detonating Jughead cancelled that out.
I, too am a Die Harrd LOSTie 🙂 and I’m not here to debate LOST, either 🙂
Everything I wrote is canon – confirmed by Damon and/or Carlton, years ago.