Christ is the true Chosen One and the true Elect. But the body of Christ is, as it implies, a corporate body, made up of many members.
When we are saved or born again by faith in Jesus, we are put into one body, the body of Christ. That is what it means to be "in Christ". All those in Christ automatically become part of the body of the Chosen One, Christ, and therefore they too are considered "chosen" and "elect". What did they do to become part of the "chosen"? They believed in Jesus.
If God only chose some for salvation and others for destruction, without them having any input whatsoever, then God does not love the whole world - He only loves PART of the world. The other part - He hates.
If that is true, and the Calvinists say that it is, then the Bible is filled with lies, like John 3:16.