We do, however, speak a message of wisdom among the mature, but not the wisdom of this age or of the rulers of this age, who are coming to nothing. 7 No, we declare God’s wisdom, a mystery that has been hidden and that God destined for our glory before time began. 8 None of the rulers of this age understood it, for if they had, they would not have crucified the Lord of glory
What was "before time began"? The "wisdom"? Or the "mystery"?
It seems that the "wisdom" and the "mystery" are not one and the same thing.
If the "mystery" and the "wisdom" are respectively the crucifixion of the Son and the mere knowledge of it (two distinct things), then it is the crucifixion itself that happened "before time began".
In other terms, the "wisdom" assumes an object of that knowledge or wisdom, precisely a "mystery", that is happened before that someone had (or: will have) that "wisdom" or knowledge about it.
Hence, since none of the Archons understood this "wisdom" about that "mystery", they crucified Jesus.
The chronological sequence is:
1) the mystery: the Archons crucified Jesus.
2) the wisdom/knowledge of that mystery: it is hidden in God.
3) "the time began": the world was created.
4) Paul and the apostles knew that wisdom. Only them and only now. The Archons are still in the ignorance.