Ok, first if i said (I may have)that the eucharist meal was a creation of Paul i misspoke. The Eucharist meal reflects a sabbatical Seder meal practiced by Pharisaic Jews. It appears that the Didache demonstrates the early christian adoption of these meals of thanksgiving. Notably in the Didache form there is no mention that Jesus shared a last meal or initiated a sacrement to be repeated nor any mention of sacrificial ransoms or covenants. It was a meal to celebrate the blessings and teachings of Jesus. Sometimes the silence is deafening.
Of course, the Eucharist reflects the seder meal. The seder meal was a part of the home Passover service! The Passover and the Eucharist are link as the Passover sacrificial meal is the prefigurement of the Eucharist sacrificial meal as was the sacrifice of bread and wine done by Melchizedek, for as the Psalmist was quoted by St. Paul: "You are a priest forever after the order of Melchizedek" (Ps. 110:4). A similarity in prayer or worship is made manifest because Christians received their liturgical traditions, at the start, from the Jews.
And the Didache does mention the sacrificial nature of this Sunday worship/meal: "On the Lord's own day, when you gather together, break bread and give thanks [Or: celebrate the Eucharist] after you have confessed your unlawful deeds, that your sacrifice may be pure. Let no one quarreling with his neighbor join you until they are reconciled, that your sacrifice may not be defilied. For this is the sacrifice mentioned by the Lord: "In every place and time, bring me a pure sacrifice. For I am a great King, says the Lord, and my name is considered marvelous among the Gentiles"" (Didache 14).
Also a eucharist appears to have existed in Ur Mark that was later slightly modified to harmonize with Corinthians. Matt simply expanded a few things and Luke (using an early form of Mark) likewise has a meal but was later interpolated using language of Corinthians. So to say that the eucharist (as a meal) was inserted into the texts is not correct.
How does it appear to be slightly modified to harmonize with Corinthians? (curious)
There is a pretty horrible fallacy in modern scholarship that similarity equals a link. This is not always so, but among some Biblical scholars, I have seen magnificently horrible leaps in logic just to "show" said links.