Christ alone does not save, it is the Triune God who saves using what Christ did for us.
Here is what happened. In Eden there was no sin. God had created it but sin was contained, and eating of the tree of knowledge allowed sin loose. Adam let sin loose in Eden. God reacted immediately with Christ paying for our sins so they do not cause our death. The salvation system used this, with the animal blood as a symbol of Christ. When blood was used as a symbol of life and Christ people were put to sleep buy still alive. When Christ died these people were able to walk the streets of Jerusalem, as Matthews tells us. God the Father saves, but it is only through Christ, Christ only saves as Christ is also God.
Read it for yourself in Genesis. God made clothing as a symbol to cover Adam, covering him from sin. Cain and Abel knew it required blood as a sacrifice for salvation, but they accepted this on faith for they did not know of Christ. Abel defied this and using his own labors, and read what happened.
Because of God using symbols instead of how I worded this because I know about Christ, it is hard to understand Genesis.