Again:
When were the Jews weak? Early in their history, before the time of David.Romans 5:
6 For while we were still weak, at the right time Christ died for the ungodly. 7 Indeed, rarely will anyone die for a righteous person—though perhaps for a good person someone might actually dare to die. 8 But God proves his love for us in that while we still were sinners Christ died for us. 9 Much more surely then, now that we have been justified by his blood, will we be saved through him from the wrath of God. 10 For if while we were enemies, we were reconciled to God through the death of his Son, much more surely, having been reconciled, will we be saved by his life. 11 But more than that, we even boast in God through our Lord Joshua the Messiah, through whom we have now received reconciliation.
12 Therefore, just as sin came into the world through one man, and death came through sin, and so death spread to all because all have sinned— 13 sin was indeed in the world before the law, but sin is not reckoned when there is no law. 14 Yet death exercised dominion from Adam to Moses, even over those whose sins were not like the transgression of Adam, who is a type of the one who was to come.
15 But the free gift is not like the trespass. For if the many died through the one man’s trespass, much more surely have the grace of God and the free gift in the grace of the one man, Joshua the Messiah, abounded for the many.
When were the Jews sinners? When they still worshiped idols.
When were "we" enemies? Jews and the nations? Well, honestly many times, but when Joshua was making war against the nations.Joshua 24:
19 But Joshua said to the people, “You cannot serve the Lord, for he is a holy God. He is a jealous God; he will not forgive your transgressions or your sins. 20 If you forsake the Lord and serve foreign gods, then he will turn and do you harm, and consume you, after having done you good.” 21 And the people said to Joshua, “No, we will serve the Lord!” 22 Then Joshua said to the people, “You are witnesses against yourselves that you have chosen the Lord, to serve him.” And they said, “We are witnesses.” 23 He said, “Then put away the foreign gods that are among you, and incline your hearts to the Lord, the God of Israel.” 24 The people said to Joshua, “The Lord our God we will serve, and him we will obey.” 25 So Joshua made a covenant with the people that day, and made statutes and ordinances for them at Shechem. 26 Joshua wrote these words in the book of the law of God; and he took a large stone, and set it up there under the oak in the sanctuary of the Lord. 27 Joshua said to all the people, “See, this stone shall be a witness against us; for it has heard all the words of the Lord that he spoke to us; therefore it shall be a witness against you, if you deal falsely with your God.”
Why did death only exercise dominion from Adam to Moses? After Moses comes Joshua.