The non-Jews found the way by which God could declare them righteous. The Jews did not succeed in fulfilling what the Mosaic laws require. Instead, they tried to find a way to be declared righteous by doing things in order that God would accept them.

Romans 9:30-33

30 We must conclude this: [RHQ] Although non-Jews did not search out a way by which God would erase the record of their sins, they actually found that way because they trusted in what Christ did for them. 31 But although the people of Israel sought a basis by which God would erase the record of their sins, they did not succeed in fulfilling the true purpose of the laws that God gave to Moses. 32 The reason [RHQ] that they did not succeed is that they did not trust that God would provide a way to save them. Instead, they were trying to do certain things in order that God would accept them. Because they did not expect the Messiah to die, the Israelites felt disgusted about Jesus’ death, which is like the stone [MET] on which people stumble. 33 This is what a prophet predicted when he wrote these words that God said about the Messiah:

Listen! I am placing in Israel [MTY] one who is like a stone [MET] on which people will stumble. What he does will offend people [DOU]. Nevertheless, those who believe in him will not be disappointed.