And a fire was kindled in their company (see Numbers 16:35, Numbers 16:40; Numbers 26:10). The flame burned up the wicked. Korah and his "company" were more "wicked" than Dathan, Abiram, and their followers, since they had received a favour from God which ought to have satisfied them (Numbers 16:9, Numbers 16:10), and since they ought to have been better instructed in the Law than ordinary Israelites.
Hence Korah alone is mentioned in Jude 1:11.