You make a good point that the idea of a Messiah is very late, and comes long after the completion of the O.T, and that all "Messianic expectations" and examples of "Messianic Prophecy" are read INTO the Text. I cannot remember the exact point that such ideas began to get traction, but not much before 300 BCE ?
Therefore all the Messianic stuff in the N.T is based upon intertestamental Rabbinic speculations and formation of new doctrines. JW Org would never acknowledge the truth of this, along with most Christians !
The practice of Eisegesis is a bad one, reading in to the text that which is not there. But in the case of our Jewish friends their development of a messiah idea probably came from their practice of midrash, adapting Scripture to tell a story and teach a lesson for the time in which they lived, so, not as naughty as the " interpretation" JW's do !
The Jews really needed badly a leader to free them under Antiochus 1V Epiphanes, hence the book of "Daniel" being written then, about 164 BCE, and Judas Maccabeus popping up as a Messiah to do the job, like a " Hammer" !