The audience of Christ's ministry, while living on earth, compared to the audience of His heavenly post-cross ministry (to Paul) is a distinction:
Concerning Christ and his earthly ministry to Israel ("the Little Flock"):
Matthew 10:5-6
These twelve Jesus sent forth, and commanded them, saying, Go not into
the way of the Gentiles, and into any city of the Samaritans enter ye
not:
6 But go rather to the lost sheep of the house of Israel.
Matthew 15:24
But he answered and said, I am not sent but unto the lost sheep of the
house of Israel.
John 4:22
Ye worship ye know not what: we know what we worship: for salvation is
of the Jews.
Acts 11:19
Now they which were scattered abroad upon the persecution that arose
about Stephen travelled as far as Phenice, and Cyprus, and Antioch,
preaching the word to none but unto the Jews only.
Concerning Paul and his apostleship to the church ("the body of Christ"):
Romans 15:8
Now I say that Jesus Christ was a minister of the circumcision for the
truth of God, to confirm the promises made unto the fathers:
Galatians 2:7-9
But contrariwise, when they saw that the gospel of the uncircumcision
was committed unto me, as the gospel of the circumcision was unto
Peter; 8 (For he that wrought effectually in Peter to the apostleship
of the circumcision, the same was mighty in me toward the Gentiles:) 9
And when James, Cephas, and John, who seemed to be pillars, perceived
the grace that was given unto me, they gave to me and Barnabas the
right hands of fellowship; that we should go unto the heathen, and
they unto the circumcision.
Romans 11:13
For I speak to you Gentiles, inasmuch as I am the apostle of the
Gentiles, I magnify mine office:
Colossians 1:24-27
Who now rejoice in my sufferings for you, and fill up that which is
behind of the afflictions of Christ in my flesh for his body's sake,
which is the church: 25 Whereof I am made a minister, according to the
dispensation of God which is given to me for you, to fulfil the word
of God; 26 Even the mystery which hath been hid from ages and from
generations, but now is made manifest to his saints: 27 To whom God
would make known what is the riches of the glory of this mystery among
the Gentiles; which is Christ in you, the hope of glory:
Ephesians 3:6
That the Gentiles should be fellowheirs, and of the same body, and
partakers of his promise in Christ by the gospel:
God’s plan was that Israel would bring the world (Gentiles) to God as His “kingdom of priests” (Ex 19:6). The “mystery” was not simply that Gentiles could be blessed, but that Gentiles would be fellowheirs, of the same body, and partakers of His promise in Christ (Eph 3:6).
Paul says his stewardship was given “to fulfil the word of God… even the mystery… hid from ages… now made manifest” (Col 1:25–27)—not through Israel functioning as the prophesied national mediating channel, but by a now-revealed administration in Christ; “Christ in you, the hope of glory” (Col 1:27), part of that previously hidden “mystery,” but now made known (Eph 3:3–6).
The result of Israel’s stumbling is Gentile salvation presently offered on an individual basis as God’s free gift by grace through faith (Eph 2:8–9), “until the fulness of the Gentiles be come in” (Rom 11:25).
Romans 11:11
I say then, Have they stumbled that they should fall? God forbid: but
rather through their fall salvation is come unto the Gentiles, for to
provoke them to jealousy.
Romans 11:25
For I would not, brethren, that ye should be ignorant of this mystery,
lest ye should be wise in your own conceits; that blindness in part is
happened to Israel, until the fulness of the Gentiles be come in.
Ephesians 3:1-9
For this cause I Paul, the prisoner of Jesus Christ for you Gentiles,
2 If ye have heard of the dispensation of the grace of God which is
given me to you-ward: 3 How that by revelation he made known unto me
the mystery; (as I wrote afore in few words, 4 Whereby, when ye read,
ye may understand my knowledge in the mystery of Christ) 5 Which in
other ages was not made known unto the sons of men, as it is now
revealed unto his holy apostles and prophets by the Spirit; 6 That the
Gentiles should be fellowheirs, and of the same body, and partakers of
his promise in Christ by the gospel: 7 Whereof I was made a minister,
according to the gift of the grace of God given unto me by the
effectual working of his power. 8 Unto me, who am less than the least
of all saints, is this grace given, that I should preach among the
Gentiles the unsearchable riches of Christ; 9 And to make all men see
what is the fellowship of the mystery, which from the beginning of the
world hath been hid in God, who created all things by Jesus Christ:
While Christ’s earthly ministry was “to confirm the promises made unto the fathers” (Rom 15:8), Paul was appointed to make known the “mystery", previously hidden, but now "made manifest” (Col 1:25–27; Eph 3:3–6). This is the stewardship given to Paul (Eph 3:2; Col 1:25), in which Gentiles are “fellowheirs… and of the same body” in Christ (Eph 3:6), a truth not previously made known “as it is now revealed” (Eph 3:5).