It is to fulfill prophecy. "As in the days of Noah".
There was much death before the rains first came. Much of the earth's population was killed BEFORE the flood.
It is much easier to control the masses in a disaster if there are less masses.
[They] know what is coming. Switched poles? Less people on earth during the apocalypse.
Less people trying to get into their bunkers? Less people trying to escape into space?