This is probably the best question any Christian could ask. Jesus was placed on this Earth for a profound purpose, which was to save all mankind.
1 Corinthians 15:22, “For as in Adam all die, even so in Christ shall all be made alive.”
This verse explains that Adam and all of his posterity were born under the death sentence. Adam was created a perfect human being and could eat from the Tree of Life. If Adam had continued to eat its fruit, he could have lived forever. (See Genesis 3:22.) However, because Adam sinned and could not eat the life giving fruit, his body slowly degenerated into death. We are all imperfect and destined to die.
Jesus came to this world to lift mankind back to perfection. How?
1 Timothy 2:5-6, “…the man Christ Jesus; Who gave himself a ransom for all, to be testified in due time.”
What does ransom mean? Ransom means “a price to correspond” to something of equal value. Jesus freely gave up his perfect human life, as payment or as a corresponding price, to ransom Adam’s life out of death. Once the ransom is applied, Adam and all his descendants will be resurrected.
Please note that both quoted scriptures state “all”. It does not state “only believers” or “who God chooses” but “all.” All of Adam’s descendants (Jew and Gentile, Christian and non-Christian, etc…) will be a part of the general resurrection.
Jesus returns a second time to restore mankind back to perfection during his millennial reign. This opportunity to regain perfect life is also called the times of restitution (restoration).
Acts 3:19-21 (KJV), “Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; And he shall send Jesus Christ, which before was preached unto you: Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.”
During Christ’s reign, the powers of earth’s sinful governments, church organizations, and social orders, will be destroyed. But the literal earth and heaven will not be destroyed. Christ will replace the current corrupt systems and will rule in righteousness. Earth will be brought back to perfection.
2 Peter 3:8-10 (KJV), “The Lord is not slack concerning his promise, …but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. But the day of the Lord will come as a thief in the night; in the which the (ecclesiastical) heavens shall pass away with a great noise, and the (social and political) elements shall melt with fervent heat (great trouble, Daniel 12:1), the earth also and the (corrupt) works that are therein shall be burned up (the fire of God’s jealousy, Zephaniah 3:8). Isaiah 4:4 (KJV), “When the Lord shall have washed away the filth…by the spirit of judgment, and by the spirit of burning.”
Soon Matthew 6:10 will be fulled, “ Thy kingdom come. Thy will be done in earth, as it is in heaven.”