Yeah, leaving Leo behind was gut wrenchingly awful, and it broke my heart. I really appreciate how realistic the break was, and the conversation that happens two years later - it felt real, not like something out of a Hollywood movie.
Well, the train was sent through echo, and unrelated to the crisis. 'It' wasn't trying to escape echo, but just passing through, therefore it was able to do so. At least, this is how I perceived it, and I accepted it without too much effort.
Why didn't they attempt to snap Leo out of it, tell him to his face that he was hallucinating?
Well, I think they reacted in a realistic way considering everything that was going on, and how traumatized they were. I was feeling a similar desperation like you - Why the hell can't chase or Kudzo just tell Leo he's going crazy?
But you know, they all were. I think we'd be surprised with our own inabilities if we were in the situation they were in. We all act differently, but we don't know how we will act. I've been through things myself, where I've gone into shock, and I can attest to this.
I was sort of assuming they talked to Leo though, when Chase was in the trailer with Kudzo and Jenna.