People only guessed because a select few pointed it out early on which made people look for clues for the reveal. The moment someone points out a theory, people start looking into it therefore making people talk about it. Word of "mouth" travels fast online. I'm not tryign to make any excuses but its obvious thats what happened last season.
Honestly, I only caught up and watched seasons 5 & 6 earlier this year in a row, avoided everything about them (I only knew Hanks was in it when I started watching) and I'd guessed it fairly quickly. I get fooled by every other twist, ever, but that one jumped out at me.
(as a side note, in fairness to the writers, I'm not convinced it was supposed to be a Shyamalan-style twist out of nowhere, which is why I think it seemed clearer than a lot of past moments where the wool was deliberately pulled over our eyes)
Anyhow, more than that particular storyline, I was referring also to the general vibes of the previous seasons. I never got the feeling I didn't know the vague direction the show was going in by the half way point - not what would happen exactly, but who the main antagonist would be, who'd be the one ending up on the table wrapped in plastic etc. With this season, I'm not even sure I'll know by the end of next week what'll be happening at the end. It's not necessarily a positive but it's refreshing.