So my theory about that Red Titan being an evolved/new type as the reason why the wall was destroyed now was correct. It certainly would not be strange for such an occurrence to happen since they are a living species.
Animesuki is strict with its spoiler policy I'll post this here instead of the thread
Originally Posted by Iron Maw
Okay, then it just makes the Titans waiting a century to attack mankind all the more baffling.
I just want to say,now that I've started reading the manga,there's a perfectly understandable reason as to why the wall wasn't broken into yet,I don't remember seeing it mentioned in episode which sorts of baffles me, maybe I missed it.
Spoiler for comparison between manga and anime:
Very early on in the manga,they mention that the titan the managed to break the wall was really bigger than any other titan they'd seen so far,the wall wasn't made to be able to resist to one that big but had resisted other attacks from smaller ones before, of course once the huge titan made a hole all the smaller ones who couldn't get in before are now able to go in