Primarily Christs ministry on earth was to his own people -- the Jews of Israel.
Jesus instructed his Jewish disciples to preach to their fellow countryman.
(Mat 10:6 ) But go rather to the lost sheep of the house of ISRAEL.(all caps mine)
Christ clearly stated this to the Samaritan women.
(John 4:22 ) Ye worship ye know not what: we know what we worship: for salvation is of the JEWS.
Our Lord was fulfilling O.T promises made to the nation of Israel.
(Rom 15:8 ) Now I say that Jesus Christ was a minister of the circumcision for the truth of God , to CONFIRM PROMISES made unto the FATHERS.
God promised his chosen people a LITERAL EARTHLY kingdom which Jesus would rule over as their king.
(Jeremiah 23:5 ) ...I will raise unto David a righteous Branch, and a KING shall REIGN...and shall execute judgement and justice in the EARTH.
(Dan 7:14 ) And there was given him dominion, and glory, and a KINGDOM, that all peoples, nations, and languages, should serve him.
Obviously the Gentiles were to be included in this earthly kingdom BUT not until the Jews accepted it first.
Ok, (Mat 5:5 ) is a description of this earthly kingdom. Also if read (Mat 6:10 )
Thy kingdom COME. Thy will be done in EARTH, as it is in heaven.
No doubt Christs disciples clearly understood that this was a earthly kingdom they were to preach.
(Luke 9:2) And he sent them to PREACH the KINGDOM of God, and to heal the sick.
The Jews rejected this kingdom and had Jesus crucified instead (Acts 2:36 ) but even then, God gave them another opportunity after Christs death, burial, and resurrection to accept this kingdom offer.
(Acts 1:6 ) Lord, wilt thou at this time restore again the Kingdom of Israel ?
We can read (Rom 11:7-12,25 and Acts 28:28 ) and see that a spiritual blindness is on Israel as a NATION for rejecting Christ as their redeemer and messiah.
Today in the church age (Eph 3:2 ) both individual Jews and Gentiles must believe the salvation gospel by faith and accept Christ as their saviour (Acts 20:24, 1Cor 15:1-4, Rom 1:16,10:9-10, and Eph 2:8-9 )
The christians ONE HOPE is to go to heaven and be with Christ after they die -- not earth ! (Eph 1:3 and 2:6 )
After the body of Christ is raptured off this earth (1Thes 4:16-17 ) Jesus Christ will return again (during the tribualtion period ) to set up this earthly kingdom and reign as king of Israel along with the faithful Gentile nations who serve him (Rom 11:26, Rev 1:7, 19:15, and 21:12 )
Hope I have been some help.