Why do the same descriptive words apply to Antiochus and to the Antichrist in Daniel's prophecy?
The same descriptive words apply because Antiochus functions as a prophetic type or picture of the Antichrist. Though historically minor, he fiercely persecuted Israel, and the traits ascribed to him—fierce countenance and understanding dark sentences—also describe the coming man of sin.
Les explains that Antiochus was a little king who barely amounts to more than a paragraph in secular history, yet he went down to Jerusalem and utterly persecuted and put tremendous pressure on the people of Israel, so in God's plan he becomes a prime player. Les says Antiochus is a picture or type of the last man of fierce countenance, the Antichrist. The only way to look at these descriptions of Antiochus the Great is that the very same descriptive words connected to him are also descriptive of this man of sin. Daniel foretold it, and it was fulfilled shortly after his visions.