From news article:
In actuality, Isaiah 53 directly follows the theme of chapter 52, describing the exile and redemption of the Jewish people. The prophecies are written in the singular form because the Jews ("Israel") are regarded as one unit. The Torah is filled with examples of the Jewish nation referred to with a singular pronoun.
Ironically, Isaiah's prophecies of persecution refer in part to the 11th century when Jews were tortured and killed by Crusaders who acted in the name of Jesus.
From where did these mistranslations stem? St. Gregory, 4th century Bishop of Nanianzus, wrote: "A little jargon is all that is necessary to impose on the people. The less they comprehend, the more they admire."