After responding to a question, Dr. Gottlieb says, "I'm going to use that question as an opportunity to speak on the targum of Divrei HaYamim; just a short introduction," and continues
Basically, nobody knows about this targum. And when I say nobody, I mean nobody. The rishonim that wrote a perush for Divrei HaYamim that appears in the Mikraot Gedolot did not use this targum, even though it existed in their day and age. Nobody knew about it. It was just an unknown - it's just one of those things that happen. "Hakol talui bemazal afilu sefer torah shebehekhal", tell us, our sages.* This targum was unlucky enough to be a targum of Divrei HaYamim. Now, nobody reads Divrei HaYamim in Hebrew, let alone the targum in Aramaic, so it just was left in the backshelves, I guess, of the libraries and not many people knew about it. Therefore, RaDaK, for example, and other mefarshim, who wrote a perush on Divrei HaYamim, when they need to prove the meaning of a word and they bring a targum, you will note, and I checked this, and I'm one of the few people today who actually study this targum and it's a topic I put a lot of time into, so when they quote a targum, they, in their perush, it is not the targum of Divrei HaYamim that they quote, it's Targum Yonatan on the parallel chapters in Shmuel and Melakhim. Each and every time that they bring a targum on one of the pesukim in Divrei HaYamim, you'll see that it's only on pesukim that have parallels in Shmuel and Melakhim.* - Found in the Zohar (האדרא רבא כרך ג (במדבר) פרשת נשא)
So nobody really knew about this targum, but manuscripts were copied over the generations. There were four manuscripts about sixty years ago, by the way, all from the thirteenth century and I say there were four, because now there are only three. This fourth manuscript happened to be in Dresden at the end of World War II and the Allies destroyed the city of Dresden and all that is left of this mansucript is like a charred, black block that cannot be deciphered in any manner or form. So that's one that's out of the question. Then, there's another manuscript that is so brittle that it can't be used either, but we have the good fortune of using a printed edition of this manuscript that was made in the eighteenth century that was made by one of the last people who was able to open it up without ruining it. So that's pretty much all we have: just these three manuscripts and some printed editions. You'll see, whoever wants to check, you'll see that there are some Mikraot Gedolot that don't have a targum at all for Divrei HaYamim. There are others that don't have the targum on the printed page of the text, but at the end of the volume, you'll get the whole targum in one block. And then there is a third group of Mikraot Gedolot editions that bring the targum on the page and they ascribe it to Rav Yosef of Sura, but I think that's a mistaken yihus. It seems almost impossible to ascribe it to Rav Yosef for linguistic reasons - I'm not going to get into that now. But what's improtant for us to know is that the enormous traeasure of information and wealth that is in this targum is basically unknown to almost all mefarshim. Only some of the very late mefarshim - when I say late, i mean in the past couple of centuries and not much more than that actually used it. and even then they didn't make full use of it.