To the Jew first, then to the Gentile. I think St. Paul said it.....
There was a very serious time line involved for every Jew of 'that generation' alive on the planet.
The urgency of the message to 'the Jew first' was 'Save yourselves from this crooked generation' (Acts 2), and 'Every soul that shall not hearken to that prophet, shall be utterly destroyed from among the people' (Acts 3).
Consider what was coming upon 'that generation':
upon you may come all the righteous blood shed on the earth, from the blood of Abel the righteous unto the blood of Zachariah son of Barachiah, whom ye slew between the sanctuary and the altar. Verily I say unto you,
All these things shall come upon this generation. Mt 23:35,36
(compare with: And
in her was found the blood of prophets and of saints, and of
all that have been slain upon the earth. Rev 18:24 )
God made sure that every Jew on earth was given the chance to 'hearken to that prophet' before the wrath came. All the Jews of that generation on earth heard the gospel, and were given the chance to repent and escape the wrath that was to come upon 'that generation', and for their progeny to avoid the curses of the OT [Lev 26; Dt 28 & 31,32] that were to come upon the race. God gave her time to repent (a full forty year generation), but she would not.