>> “It was a MYSTERY, hid in God from the foundation of the world” <<
.
The Mystery that Paul solved was the remarriage of Yeshua to the same bride he divorced for her iniquity, now made permissible under Torah by the husband’s death for her sins.
Yes, it was indeed the purpose of Paul’s ministry, and the reason Paul had been prepared by Yehova at the feet of Gamaliel. The gentiles to which Paul was called were the out of covenant lost sheep of the House of Israel, living dispersed along the northern shore of the Mediterranean.
I would love to see the scripture backing for that assertion! Here is the mystery explained, in Paul's own writing:
Ephesian 3:3 that is, the mystery made known to me by revelation, as I have already written briefly.
4 In reading this, then, you will be able to understand my insight into the mystery of Christ,
5 which was not made known to people in other generations as it has now been revealed by the Spirit to God’s holy apostles and prophets.
6 This mystery is that through the gospel the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus.