Blessings of Christ's Death before we believe !
For whomever Christ did die for, the following is True of them no matter what, either before and after conversion, meaning before and after they become believers !
First, its True that He indeed died for them, both in their stead as a substitute and on their behalf, or for their good 1 Pet 2:24
24 Who his own self bare our sins in his own body on the tree, that we, being dead to sins[By His Death for us], should live unto righteousness: by whose stripes ye were healed.
Secondly, For all whom He died, He also arose, because of their Justification Rom 4:25
25 Who was delivered for our offences, and was raised again for[Because of] our justification.
Many do celebrate easter , supposedly commemorating the Lords Resurrection, but very few understand the True significance of that Blessed Event, for it was the evidence that all for whom Christ was delivered for their offences, that they are now Justified before God ! Yes, even before they believe !
Thirdly, For them, He sits on the Right Hand of God !
Fourthly, He makes intercession for them, and all this is witnessed to by the Apostle here Rom 8:33-34
33 Who shall lay any thing to the charge of God's elect? It is God that justifieth.
34 Who is he that condemneth? It is Christ that died, yea rather, that is risen again[For our Justification], who is even at the right hand of God, who also maketh intercession for us.
This making Intercession, Isaiah wrote of the same Isa 53:12
12 Therefore will I divide him a portion with the great, and he shall divide the spoil with the strong; because he hath poured out his soul unto death: and he was numbered with the transgressors; and he bare the sin of many, and made intercession for the transgressors.
You see that ? He made Intercession, not for the believers, but for the transgressors, those He bare their the sins, the many ! Any Transgressor Christ makes Intercession for shall be saved by His Life, shall come to God by Him Heb 7:25
25 Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them.
Isaiah's here by prophecy is speaking of Christ's Priestly Work for those only that He Represented, the Israel of God, and this Work Justifies them before God or accounts them as Righteous, Yes even before they believe, because its not based upon their believing, but upon Christ bearing their sins !
Notice how Isaiah under inspiration of the same Spirit as Paul, did link together, the bearing of sins, and the making of Intercession in either case this is Priestly Work done by Christ for those He died for before they believe !