I personally think that the
are his. I mean there we're 3 bunkers and from memory 3 explosions. The timing seems all too perfect, and why didn't they go off in any other of the endings. (This could be my stubborn attitude toward religion mind.) Like he had spotters with the detonator just encase you won the ensuing battle against him. Isn't there also a point about a jammer preventing any radio calls in and out of the valley? What if the really cool fucking music radio stations belong to edens gate too to deliver some fake news to attempt to subvert people toward the cause. I mean given the games somewhat political nature I wouldn't disregard such an idea.
tdlr - I think big joe sets em off