“Why were Korach and his followers punished by being swallowed up by earth?  Because Korach and his congregation fought against Moshe, who, as the pasuk describes, was ‘more humble than anyone on the face of the earth.’  If so, there was no other place for Korach and his followers to descend other than underground.” – R’ Zev Wolf of Strikov zt”l taken from Torah Tavlin.