I just found a pretty sad theory to explain the Weak music video if you JUST think about the MV
So the MV starts with us seeing all 3 brothers, except Ryan and Adam aren’t waking up. They look dead, even. Jack isn't dead, presumably because he refuses to. He then sees the light(if you don’t know what that means, seeing the light is when you finally understand something/realize a truth.) In the front of the train. He hesitates, looking back at his brothers, when he gets a push forward. He starts to walk forward on his own, and we even see Ryan and Adam flash in and out of sight, which for the sake of this theory I will say is because they are dead and are trying to guide Jack towards the light and follow them.
When he gets to the next cart, the doors open right as he is about to pass them. Jack doesn't hesitate at all to leave the train, wanting to continue to "live" in whatever form he is in between life and death, but something stops him. Jack tries to get out, punching at the barrier and screaming at the passers-by, but they don’t see him. Heck, they don’t even hear him, which correlates to Jack being a ghost in between life and death. The train doors shut, and Jack is getting thrown around. Suddenly, the emergency lights come on, and Jack is thrown to the ground. Jack gets himself together, and the emergency lights turn off. Jack then realizes that the light is where he wants to be, and he goes forward, and smiles when he sees that the light is in the next cart. The light suddenly gets extremely bright, and that's when Jack turns around and sees that he's on a train track. Then he turns around again, and suddenly he gets hit by the train he was on, finally taking him to death.
The train is the path Jack needs to cross in order to finally get rest, but the train tries to get him off with different things,(opening the train doors, throwing him to the ground when the emergency lights where on,) but some divine power is guiding him through it by showing him a light at the end, setting a barrier up by the doors to stop him from exiting, and giving him the motivation to get up when he got thrown down to the ground. He makes it to the light, and can finally rest with his brothers.
This was just a random idea I had lol, but I think it's really fun to theorize about stuff like this!