And then he attested its validity with the words, "This is the blood of the covenant commanded by God."
He did the same thing with the place of worship and its furniture.
Moses said to the people, "This is the blood of the covenant God has established with you." Practically everything in a will hinges on a death. That's why blood, the evidence of death, is used so much in our tradition, especially regarding forgiveness of sins.
That accounts for the prominence of blood and death in all these secondary practices that point to the realities of heaven. It also accounts for why, when the real thing takes place, these animal sacrifices aren't needed anymore, having served their purpose.
For Christ didn't enter the earthly version of the Holy Place; he entered the Place Itself, and offered himself to God as the sacrifice for our sins.
He doesn't do this every year as the high priests did under the old plan with blood that was not their own;
if that had been the case, he would have to sacrifice himself repeatedly throughout the course of history. But instead he sacrificed himself once and for all, summing up all the other sacrifices in this sacrifice of himself, the final solution of sin.
Everyone has to die once, then face the consequences.
Christ's death was also a one-time event, but it was a sacrifice that took care of sins forever. And so, when he next appears, the outcome for those eager to greet him is, precisely, salvation.