Ok, well the picture guide is referring to the big long story by Abnett and Lanning (DnA), and even though it's a bunch of separate titles (Guardians, Nova, War of Kings etc), it's essentially one big story, right? That story ended when DnA ended their run. A little while later, Jonathan Hickman started his F4 run and picked up the loose threads with the Inhumans and used them for his own story. Even though it features some of the same characters, it's an entirely different story by a different writer. By Infinity he's done a huge amount of work on the Inhumans, so their scenes actually have a lot of weight if you've been reading F4 and New Avengers, but it's also tying up the first half of adjectiveless Avengers and introducing Thanos as a wildcard that he's probably going to start paying off very soon. Thanos being in Infinity doesn't mean it's a sequel to his last appearance, basically.
Superhero comics like this aren't really a continuous universe even though they pretend to be, so I find it best not to stress over how characters like Thanos get from one story to another. Separate stories, shared characters. It's fun.
Edit: also holy crap did you read all those books at that Infinity link? It blows my mind that people are recommending an endurance slog of reading like that to new readers. Because if I had to read all that I think I would hate comics afterwards, it would seem so complicated. Comics tie-in marketing is harsh to newbies, it's kind of gross now that I think about it. Been reading so long I can tune it out now, like static noise.