The problem with prequels for something like GoT is that you already know the long term ending. It's not as if there was some other wacky plot thread that went on that we don't already know the resolution for. So while in the episode to episode sense you can maybe build drama at some point, probably pretty early on, it's going to turn into what's the point?

You can't say the early season of GoT were just about politics when the show opens on the Whitewalkers and clearly sets up a large overarcing plot very quickly that relied entirely on not knowing what the ending would be. House of Dragons won't have that because no matter what happens you know what the worldstate will be in the end and it just turns into watching it play out and lead to a known ending eventually.