Even today, are not Jesus' believers predominately Gentile, with Messianic Jews being a disproportionate minority? We are living in the Church age, which is predominately Gentile.
Isaiah 65
[1] I am sought of them that asked not for me; I am found of them that sought me not: I said, Behold me, behold me, unto a nation that was not called by my name.
That thinking is just evidence of listening to men's doctrines spewed by Biblically illiterate preachers that don't study all The Bible, but are just focused on a specific set of doctrines promoted by their denominational organization. Concerning the Jews, one of their illiterate doctrines is with wrongly thinking that all Israelites are Jews.
The name Jew was used by those of the southern "kingdom of Judah", also called the "house of Judah" in God's Word. It was not a label used by the northern ten tribe majority of the "kingdom of Israel", also known as the "house of Israel" after the split of old Israel.
The believing Jews are a minority in Christ's Church compared to the number of Gentiles simply because God promised Judah would not lose their heritage as being of the old nation of Israel. This is why the Jews, even Messianic Jews, still stress the law, and God's holy days, etc., not in order to be saved against The Gospel, but because of their Jewish heritage. It is how they, and the world, knows they are the Jews.
But for the lost ten tribes of Israel, called the "house of Israel" in God's Word after the 1 Kings 11 split, God prophesied that they would lose knowledge of their heritage as part of old Israel. God scattered them to Assyria and the lands of the Medes, among the Gentiles, and they became 'as'... Gentiles. And the ten tribes actually made up the majority of the seed of old Israel.
Bible prophecy and history shows that the majority of the ten northern tribes of Israel were scattered further into Asia Minor and Europe. And they brought their Baal idol worship which God had removed them for, with them in those new western lands. And then miraculously, when Jesus Christ was rejected in Jerusalem, and was then preached to those western nations, they began to put away their Baal idols and became the western Christian nations of history.
That fulfilled God's prophecy to Jacob that his seed would become "a nation, and a company of nations" (Genesis 35). And to Joseph's son Ephraim, that nations prophecy continued, as Ephraim's seed was to become "a multitude of nations" (Genesis 48).
Gen 35:10-11
10 And God said unto him, "Thy name is Jacob: thy name shall not be called any more Jacob, but Israel shall be thy name": and He called his name Israel.
11 And God said unto him, "I am God Almighty: be fruitful and multiply; a nation and a company of nations shall be of thee, and kings shall come out of thy loins;
KJV
Gen 48:18-19
18 And Joseph said unto his father, "Not so, my father: for this is the firstborn; put thy right hand upon his head."
19 And his father refused, and said, "I know it, my son, I know it: he also shall become a people, and he also shall be great: but truly his younger brother shall be greater than he, and his seed shall become a multitude of nations.
KJV
It doesn't require much thinking to understand that the nation of Israel has only ever been but one... nation in the holy land. So when The New Covenant Jesus Christ manifested, and the area of the western Christian nations was the result, it shouldn't be that difficult to understand that "company of nations" and "multitude of nations" prophecy was fulled in Christ Jesus in those western nations of Asia Minor and Europe.
If the Biblically illiterate preachers that claim all the seed of Israel are Jews would study more of their Bible and Biblical history, they would not make the ignorant mistake of claiming the migrations of the ten lost tribes was about Jews, but instead about Israelites that lost their heritage as Israel, and became as GENTILES.
So when speaking of Christ's Church today being made up of a GENTILE majority, the Biblical truth of the matter is that the majority of believing Gentiles in the early Christian nations were ISRAELITES of the seed of the northern ten tribes that God scattered first to the West. This is actually one of the things God talks about revealing on the last day of this world, per the Ezekiel 39 Scripture. He showed on that final day, the "house of Israel" (ten tribes) would then know that He scattered them because of their false worship against Him.
As of today, the majority of the descendants of the ten tribes don't know their heritage from old Israel; they actually think they are GENTILES. That is where the term 'lost' became used for the ten tribes, as the Lost Ten Tribes. Can't call them Jews, because the Jews are not Lost as Israel.