Through His example others can become righteous to. You missed the aspect, which I am really trying to understand through your mind, that Adam made many people sinners. He did not show them how they could sin, but actually made them sinners. The disobedience of one made many sinners. Death, to a Baha'i, is a spiritual and not a physical condition.
Phsyical death is a shadow of spiritual death, yet BOTH came by sin.
Rather boring if you ask me. A phsyical body bereft of sin would be a glorified body. And the devil said unto him, If thou be the Son of God, command this stone that it be made bread.