1Co 15:3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; 1Co 15:4 And that he was buried, and that he rose again the third day according to the scriptures: Paul receive this Gospel from Christ: Gal 1:12 For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ.
It was God's choice to bestowed His Grace on us. The Bible tells us that He is not willing that any man perish, 1Ti 2:4 Who will have all men to be saved, and to come unto the knowledge of the truth. 1Ti 2:5 For there is one God, and one mediator between God and men, the man Christ Jesus; 1Ti 2:6 Who gave himself a ransom for all, to be testified in due time.
The fact that He died for all is proof He desires their salvation. "All" are included in the finished work of Christ: His death, burial and resurrection, 1Co 1:30 But of him are ye in Christ Jesus, who of God is made unto us wisdom, and righteousness, and sanctification, and redemption: 2 Co. 5:14 For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead: 2Co 5:15 And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again.
If Christ did not die in place of the "all" then the "all" cannot be said to have died. But, It is no longer an "if." Christ did die for all, therefore, all had their sins paid for in Christ and therefore all are dead in Christ. His death is just the same as if we all died.
To believe God is our responsibility, It is God's choice to redeem; it is our choice to believe! "We thus judge" meaning we have come to a conclusion - a settled truth as we consider the provision of Christ. All that Christ did, His entire purpose for coming into the world, included and blessed all of mankind. Col. 2:13 "And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;" Therefore, "....that if one died for all, then were all dead:" not just dead in sins but now all included in Christ. "For as in Adam all die, even so in Christ shall all be made alive." 1 Cor.15:22. When Christ died on the cross we died with Him.
You know the sad truth is that man has been duped by satan. God has reconciled all humanity to Himself, 2 Co_5:18 And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation;2 Co_5:20 Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God. But the masses of people don't seem to care about eternity! Living for the temporal but the Bible warns us to look for the eternal. 2 Co 4:18 While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal. The word "while" says, "don't let your days, weeks and years be lost in that which has no eternal value. While you are waiting to decide time waits for no one, 2Co_6:2 (For he saith, I have heard thee in a time accepted, and in the day of salvation have I succoured thee: behold, now is the accepted time; behold, now is the day of salvation.) You can believe on Christ now for eternal life!