It's pretty safe to say there's a plan. It started with Erwin revealing publicly the goal. It continued with the decision to push forward despite the catastrophic casualties due to the abnormal titan. Thus it's safe to say the forest is no coincidence. Nobody knows shit because there are traitors among them, as slaying the two captive titans proved. Although it would make sense for Levi to be in. It might be too hard for Erwin to control everything by himself.

What annoyed me the most during this episode, in addition to people willingly getting themselves killed, is Eren. He was supposed to be an obsessed, almost homicidal titan-killer, but now he's like any regular greenhorn scared next to witless. He should be trembling from anticipation and fuming because they are held back, not given the permission to attack.