We Christians have to defend Matthean priority because, to our great surprise two thousand years later, the credibility of the entire religion depends on it. If Matthean priority is false, then Jesus did not rise from the dead, and what John and Luke promised that these things are written for you to know the certainty of them is a lie. This is not the obvious conclusion of Markan priority, and it sounds absurd on its face, but scholars have rightly drawn that line of conclusions. They reject Matthean priority because Matthean priority, and only Matthean priority, means that Jesus is who the gospels say he is. https://orthodoxreflections.com/why-matthean-priority-matters/