Imagine that we knew nothing about Christ - that his life had been obscure, that there had been no gospels, that all evidence and memory of him had been lost.
Would the existence of Jesus then have any value?
Yes - because the birth, death and resurrection of Jesus Christ was of objective, cosmic significance - even if nobody alive knew anything about it!
In other words, Christ achieved at least two things which have permanent and universal value even if we know nothing about them: he took away the sins of the world; and he made it so that when every person dies he or she will be resurrected.
Those who knew or currently know nothing of Christ during mortal life, will be made aware of these true facts after their death; and will face a decision and judgment about whether they accept Christ's offer of salvation.
This is simply a fact of reality, independent of human knowledge, belief or experience. This is the cosmic, objective significance of Christ.*
*There is, of course, a lot more to Christ than this! But this much is given.