Why?................to make it a kind of Rorschach test for the Pharisees, Saduccees, and Jewish Scribes when Jesus finally came onto the scene. Think about it. If the Pharisees and their Jewish compatriots had recognized Jesus as being a complete fulfillment of all of the various Jewish expectations that danced about in the collective, apocalyptically inclined Jewish imagination -- i.e. as Shiloh, as the Branch, as The Prophet, as The Son of Man, as the Messiah (see F.F. Bruce and also Kaiser, Jr.), -- then they wouldn't have contemplated finding a way from Scripture to have Jesus put to death as a 'false prophet,' a designation which, as you know, many non-Christian Jews still think Jesus is classified by today.
But we all know from the contexts of Scripture (Deuteronomy 13 and 18) that the Pharisees did have at least some reason to make a Scriptural diagnoses about Jesus' character, and by interpreting all of what transpired with Jesus through the various
strange networking hermeneutics by which Jews wrote and have interpreted their Scriptures and their identities within their respective religion (see Neusner), they did have partial justification for calling for the death of Jesus---------------------but only if He was perceived and interpreted through an utterly self-willed,
truncated hermeneutic that refuses to painstakingly sift through and take everything in Scripture into account in its totality.
In essence, it means that God brought about His will by utilizing the partial blindness of the Pharisees as they attempted to rationalize their assessment and identification of Jesus. They would inevitably fail and apostasize due to their emotional states and their penchants for sustaining their interest in political and social power (something they were highly mindful of and invested in on a day by day basis since they always had their Roman overlords standing over their heads, reminding them of their forced subjugation.............) Basically, God forced them into a catch-22 and orchestrated the forcing of their hands against Jesus through their partially blinded attempts to justify themselves against Jesus on the one hand......and against the Romans on the other hand.
So, of course, how one interprets the figure of "the Prophet" in Deuteronomy 18 will depend on one's emotional state and one's vested interest at the time of doing so; and as Zimmerman points out, the personal hermeneutics which we each apply to varying degrees to our outlook on life, to our understandings of meaning in the world, and even to how we interpret the Bible, are all always interest driven. It's inescapable.
[Note: the above is my own interpretation of the Rorschach type situation that I believe God brought about in Jesus, it isn't something that Jacob Neusner even touches upon, as far as I know.]
References
Bruce, F.F. (1995/1978). The time is fulfilled. Grand Rapids, MI: William B. Eerdman's Publishing Company.
Kaiser, Jr., Walter. (1995). The Messiah in the Old Testament. Grand Rapids, MI: Zondervan Publishing House.
Neusner, Jacob. (1991). Judaism as philosophy: The method and Message of the Mishnah. Columbia, SC: University of South Carolina Press.
Neusner, Jacob. (2004). Judaism and the Interpretation of Scripture. Peabody, MA: Hendrickson Publishers.
Zimmerman, Jens. (2015). Hermeneutics: A very short introduction. Oxford, UK: Oxford University Press.
(In fact, if you really want to get into a deeper understanding about the Jewish rational mindset, which is somewhat different than the Greco-Roman form of rationality, you can't go wrong with anything written by Jacob Neusner).