So God lied? The covenant with Israel was not everlasting?
Yes, it's everlasting. However, that's often misstated. God said that it would be everlasting as long as they followed him. They didn't. They followed the pagan gods of Canaan and then they formed what amounts to their own religion, well away from what God set down for them. They refused to accept the messiah that God had promised to them. Jesus tried to lead them back to God and they killed him, as prophesied. It was the Jews who broke the covenant, not God.
Maybe it was some Jews that rejected Him. Jews lined the road praising Him as he came into Jerusalem the last time and took over the temple. There was apparently a full scale insurrection that week that is not covered in the very brief account of what went on those few days. The Jewish hierarchy and the Roman forces must have brutally put down the uprising. The bible is notable for its brevity in complicated events.
In any case not near all Jews rejected Jesus and the first Christians were Jews both in Jerusalem and Asia Minor (Turkey today).
It is to be noted that the Jerusalem Christians and the Christians of Asia Minor rejected Paul and the Roman church adopted him after some alterations to his letters and the forgery of 2nd Peter.
It was the Roman church masquerading as Christian that disowned the Jews, not God, not Jesus.
Patriotism (and religion) is the last refuge of a scoundrel. Jesus: "Take heed that no man deceive you." Hebrew Roots Judaizer
