There is not enough meat to that letter to make a 1,000 word column. That's the most likely reason it's not in the news. Interesting to people who would like a chance to analyze DM and a lot of nothing to everyone else.
I do want to point out DM has rather distinctive f's and really regular form in his letters. The descending strokes of his j and g are jug shaped, while he uses a straight stroke to make his y's. Half the time his I's and t's have a curl to the right at the base. Vertical strokes are quite vertical though d's in particular slant left. In short there are a lot of obvious quirks that would make his writing recognizable.
If of course it is his, ..... but even if it was.... the letter is a non starter IMO..... nothing of any importance IMO... JMO