Hezbollah pagers explode across Lebanon causing thousands of casualties. This is genius! I would like to know how the pagers were distributed en masse and what triggered them to explode.

I assume Project Eldest Son with a tweak. (Which itself was merely an iteration on the concept of sabotage as old as contaminating the enemy camp's water source.) I assume they created a pathway into the enemy's supply chain, who then distributed the batch of IED pagers which were set to detonate on a specific signal - likely a 3 sec delay after a specific phone # (given reports of hand and face damage).