God privileged Israel above all the Gentile nations. They were known as God’s chosen people and He made them special to Himself (Deut. 7:6-8). They were trusted with the oracles of God (Rom. 3:2) as well as the covenants, the law, the service of God (priesthood), the glory and manifested Presence (Rom. 9:4). God tested the responsibility of the Jews in two specific ways: first, by giving them His law to obey; finally, by sending His Son to them as their promised Messiah. Israel miserably failed in both. Because they represented mankind, when they crucified their Messiah, God condemned the entire human race born in the first man, Adam. At this point probation was over; God had proved His point.

Articles that further detail this topic:

https://www.reintgenchristianbooks.com/mankinds-probation-purpose/

https://www.reintgenchristianbooks.com/chapter/chapter-dispensation-depravity/

https://www.reintgenchristianbooks.com/what-is-the-jewish-dispensation-and-what-are-its-important-principles/