Romans 9 teaches Conditional Election based upon Faith and Conditional Reprobation based on Unbelief:
Rom 9:30 What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith. 9:31 But Israel, which followed after the law of righteousness, hath not attained to the law of righteousness. 9:32 Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone
Wherefore: διατί – through, by, with, because of, for the sake of
Why were the Israelites cut off? Because of their unbelief.
Why were the Gentiles grafted in? Because of their faith.
That is what Paul taught in Romans 9.
FREE BOOK ON THE DOCTRINE OF FREE WILL