The second Age is the time of the fall of Numenor, the Elvish split over Sauron and the creation of the Rings, the setting up of Arnor and Gondor and the Last Alliance.
There's political intrigue, world altering cataclysms, gigantic battles, betrayals, power... Quite a lot of fodder for great TV.
Maybe they haven't even read LOTR
Actually I've never read Unfinished Tales. I really need to do that.
It was around when the movies came out. I had gotten into reading a lot of LotR fanfics, and decided to learn everything I could possibly cram into my brain about the setting.
The databanks are a little rusty, but still retain a lot of random little factoids. Like Melkor having raped to sun in one version of the tale, to an Ainur's power being finite and depletable.
As I said... The Second Age is kind of just skimmed through for the most part. Even the Third Age had more narrative forces on events that happened, and hardly anything of real import even HAPPENED in Third Age until the end.
Meanwhile, you have the ridiculously short First Age setting over there stuffed to bursting with nigh all the really cool stories.
... And as an aside, personally, it doesn't really help matters that Numenor fits with the greater story about as well as The Hobbit does. Worse honestly, and for much the same reasons.