Let's make it simple here then.
I believe the leaders of Israel, the Sanhedrin etc, could have exercised their free will and accept Jesus as their Messiah, whether was it when Jesus was in the flesh, or finally, when Stephen was preaching to them in Acts 7, under the inspiration of the Holy Spirit.
But in both cases, they rejected the gospel of the kingdom. When the Son preached to them, they reject, when the Holy Spirit preached to them thru Stephen, they reject.
In both cases, they killed the messenger. That signaled the rejection of the Trinity, the final act in Acts 7 meant they rejected the Holy Spirit.
God foresaw that from the beginning yes, no one is denying that. My point is that they could have accepted Jesus as their promised Messiah at any point of time. God foreknowledge did not predetermined that they had to reject.