Pure speculation but I heard a rather relevant quote recently that went something like

"The reason the Palestine conflict is so difficult to resolve is because of the power imbalance. One side holds all the power and is therefore unwilling to do any concessions"

By leveling the world's and Paradise Islands population to equal numbers this power balance would be restored and thus both parties would now be open to peace talks

*disclaimer not sure if this is the correct interpretation, just my own.