Yes like I said they did not atone, but they covered sin temporarily, and allowed someone entrance to abrahams bosom. Again it's absolutely impossible to believe by faith in Christ, when he was not manifest yet, or to believe in a resurrection that had not happened yet. When Christ decended He preached the gospel to those in abrahams bosom so they could go to heaven, and declared victory over the grave and hell. For until that time, even angels did not know about grace. That means that even angels accepted that sacrifice was all their was to avoid hell. Furthermore, even if they had faith in God if they did not sacrifice as per levitical law, they would go to hell. Hell is described all over the old testament.
Here are some quotes from some theologians on this matter:
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Walter Kaiser (b. 1933) clearly overstates the case in arguing that “the object of the OT believer’s faith was no different from our own except fro the fact that his [the object’s] name was not yet announced as Jesus” (SOT in JBT, 11). This is the typical Reformed covenantal position. John Calvin said, “The covenant made with all the patriarchs is as much like ours in substance and reality as the two are basically one and the same” (as cited in Feinberg, CD, 169). Charles Hodge likewise saw no basic difference between the content of the gospel necessary to believe for salvation in the Old Testament and that in the New:
The Redeemer is the same under all dispensations. He who was predicted as the seed of the woman…is our Lord Jesus is Christ, the Son of God…He, therefore, from the beginning has been held up as the hope of the world, the SALVATOR HOMINUM. (ibid, 170)
HOWEVER , THIS CONCLUSION IS NOT BORNE UP BY THE BIBLICAL EVIDENCE. As Allen Ross notes, “It is most improbable that everyone who believed unto salvation [in the Old Testament] consciously believed in the substitutionary death of Jesus Christ, the Son of God” (ibid.). John Feinberg (b. 1946) adds, “The people of the Old Testament era did not know that Jesus was the Messiah, that Jesus would die, and that His death would be the basis of salvation” (ibid., ibid., 171)."
Now normally I would take charles ryries position or norman geislers position on this, however I simply don't think faith in Christ was required in the old testament, maybe faith in God and that God is good and gracious. But still it was very clear that if you didn't sacrifice God would Judge you strictly, killing off your nation bit by bit. Allowing the enemy to conquer you or falling to starvation or other calamity. I am not sure if the sacrifice took away sin but it covered sin so that you were not punished for your sins until the covering was removed, meaning if you died after you sacrificed you were not technically seen as a sinner and you would be in paradise instead of hell where the rich young ruler was.