This so called “triumph” that Ralph, Simon and Jack feel differentiates from the slight triumph that Ralph and Piggy felt when they found the conch shell. Ralph, Jack and Simon’s feeling of triumph comes from the absolute destruction they create. When Ralph and Piggy grabbed the conch shell they used a sapling that was on it’s last legs to retrieve it, so in order to not destroy the sapling they had to to keep a level of gentleness. When the three boys pushed this rock over gentle was the last word on their minds when faced with this “challenge”. The force of the rock falling caused a deep hole in the canopy of the forest and clouds of dust. And for what reason? Pushing this rock over did not serve much purpose, they just wanted to see if they were able to do such a large task with only the strength of three little boys. They found triumph in succeeding. When Ralph retrieved the conch it served a purpose, although to Ralph at the time it just seemed like an interesting toy, it did prove to have some benefit to them.
The idea of destruction in this book is commonly viewed as an act of God, this is ironic considering that according to the Catholic faith God is in fact the creator. But, this view on God in relation to destruction why these boys felt such triumph in shoving this rock over a cliff. They had created such powerful force with such a startling effect. That may have made them feel god-like and powerful. Especially with the timeline of this book, having the boys living in a world that was currently in war, pure terrorizing of their surroundings was proving to be powerful and “effective”, and they were witnessing that first hand. Causing this wreckage Maybe even made them feel grown up being able to succeed in an act that requires so much strength.