Was the mystery of Christ known to people in earlier generations?
No. The mystery of Christ was not known in earlier generations. The context says it was not made known to the sons of men in other ages, and that this secret had been hidden in God from the beginning of the world, from Adam. It was veiled and covered up until revealed.
Les explains that the mystery was an unveiling—something kept under wraps that was suddenly made known by revelation to the apostle, so that readers could understand the knowledge in the mysteries, or secrets, of Christ. In verse 5, in other ages or generations it was not made known unto the sons of men, but it is now revealed. Verse 6 shows that the Gentiles should come in under God's grace. Verse 9 says the fellowship of this mystery, or secret, from the beginning of the world, that is from Adam, had been hid, veiled, and covered up in God, the same God who created everything through Jesus Christ. So there was a time when no one knew these things.
Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
More Questions
Does Ephesians 3:5 say the mystery was made known or not made known to men?
Ephesians 3:5 does not say the mystery 'was made known'; it says these things 'were not made known to the sons of men' but are 'now revealed.'