We know the Last Supper originated as a dream Paul had.
Remember the four Gospels were composed AFTER the letters of Paul.
Paul says he received the Last Supper info directly from Jesus himself, which indicates a dream.
1 Cor. 11:23: "For I received from the Lord that which I also delivered to you, that the Lord Jesus in the night in which He was betrayed took bread"
The Gospels take Paul's wording and inserts disciples of Jesus.
However Paul faked this dream.
Translations often use "betrayed", but in fact the word paradidōmi means simply ‘hand over, deliver’. The notion derives from Isaiah 53.12, which in the Septuagint uses exactly the same word of the servant offered up to atone for everyone’s sins.
Paul is adapting the Passover meal. Exodus 12.7-14 is much of the basis of Paul’s Eucharist account: the element of it all occurring ‘in the night’ (vv. 8, 12, using the same phrase in the Septuagint, en tē nukti, that Paul employs), a ritual of ‘remembrance’ securing the performer’s salvation (vv. 13-14), the role of blood and flesh (including the staining of a cross with blood, an ancient door lintel forming a double cross), the breaking of bread, and the death of the firstborn—only Jesus reverses this last element: instead of the ritual saving its performers from the death of their firstborn, the death of God’s firstborn saves its performers from their own death. Jesus is thus imagined here as creating a new Passover ritual to replace the old one, which accomplishes for Christians what the Passover ritual accomplished for the Jews.
There are connections with Psalm 119, where God’s ‘servant’ will remember God and his laws ‘in the night’ (119.49-56) as the wicked abuse him.