The wicked of the last days are not to be wiped out in one cataclysmic catastrophe. There will be wars, famine, plague, earthquake, thunder, lightning, etc. It is wisdom in God that the bad are not cleared away all at once. This is the same time period spoken of in the parable of the wheat and the tares:
'But behold, in the last days even now while the Lord is beginning to bring forth the word, and the blade is springing up and is yet tender—
Behold, verily I say unto you, the angels are crying unto the Lord day and night, who are ready and waiting to be sent forth to reap down the fields;
But the Lord saith unto them, pluck not up the tares while the blade is yet tender (for verily your faith is weak), lest you destroy the wheat also (DC 86:4-6).