Not quite true. Though the RCC has not been so kind as to preserve their writings for us, we know that Messianic Jews, called Nazarines, existed in numbers right up through the fourth century. Shlomo Pines has found further evidence that they in fact survived until the 11th Century at least.
When the Inquisition broke out in Spain, its primary targets were Jews who had converted to Christianity while trying to keep their Jewish, Torah-based customs. So we know that there were what we might call "Messianics" then too.
Martin Luther wrote a pair of tractates in his own time called Against the Sabbath Keepers and Against the Judaizers. I don't think he would've found it necessary if there weren't those who were keeping the Sabbath and the "Jewish" Torah-commands.
My own Pilgrim ancestors had great regard for the Torah. They even originally set up Thanksgiving in October, and created it after the pattern of Sukkot (the Feast of Tabernacles).
I can't prove it with 100% certainty, but it seems to me that those we would call Messianics today--men and women who believe that Yeshua HaMashiach, Jesus the Christ, is the Son of God and Redeemer of the World, but who also saw that God never abridged the Torah--have always been around. Heavily persecuted and forced to keep their heads down, but there nevertheless.
This was not due to any institution of Man, but rather, I believe, through the Holy Spirit writing the Torah on our hearts (Jer. 31:31-32, Ezk. 36:26-27, Heb. 8:8-12). Today's Messianic movement did not appear under any one leader, but was a spontaneous movement of the Spirit through the hearts of thousands of people who had never met, spread out around the world.
That's not to say that we're perfect or have completely recaptured the essence of the 1st Century Church, nor is it to say that all true Christians are Messianics or vice versa. We have our own problems. But the idea of being fully Christian and Torah-observant at the same time is nothing new.
Interesting view of History of the Gaps - impossible to prove or disprove. In your version: Except for those who kept their heads down, and about whom we have little record, the rest of Christianity went bad real early for you.
But I still have the same question, when did you guys, your church, come along and get it right again?