The correct meaning of the passage is that blindness has happened to part of Israel. Not part of the reason, part of Israel.
Much love!
That is an opinion, without Scripture to prove it.
But there is Scripture proving it
must be 'part of the reason':
For God hath concluded them all in unbelief, that he might have mercy upon all...for we have before proved both Jews and Gentiles, that they are all under sin. (Rom 11,3)
They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. (Rom 3:12)
All were judged guilty. None stood with Jesus in the end. They all turned back from Him. At time of the cross, the Scripture of prophecy was fulfilled, in that none on earth had the faith of God, nor did His will. And all they that had the profit of the oracles of God (Rom 3:1-2), had all become unprofitable to God.
Blindness happened to all Israel, when the Redeemer out of Sion came to the first as promised, and now all Israel is saved: all that are of Israel are not Israel, because all that are in Israel of God are saved by grace through the faith of Jesus. There are no more of Israel that are not Israel (Rom 9:6), as there persistently was, when the children of Israel were only born and circumcised after the flesh, but not of heart after the Spirit, as was Isaac. (Gal 4:28-31)
That old seed of promise by flesh is still beloved for the fathers' sake, even as any seed of flesh on earth, and so they can be grafted into the Israel of God, as all on earth can: by repenting and believing Jesus.
Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called. That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed. (Rom 9)
Are not the children of the promise, the seed of promise as Isaac was? Is not the seed of promise born after the Spirit and not after the flesh? Are not they born of the God of Israel, of Israel? What are the uncircumcised coming in to by circumcision of the heart in the spirit of Christ? Is not the holy olive tree of the God of Israel, the Israel of God?
If these questions are answered in the negative by proof of Scripture, then my conclusions are false. If not, or if not answered at all, then they stand true, and the natural conclusions from them are true.
No one has even tried to answer them, because they cannot be false. They are obviously true according to Scripture.
Giving up long-learned and earnestly sought for traditions of prophecy is for some impossible, so that even Scripture is not allowed to get in the way of them.
I am blessed. Only plain Scripture with plain meaning is all that matters to me: the truth of God and the doctrine and prophecy of God. And my own long studied favorite ideas must be done away, when God demands it by His Word.