Ken nods, reassured that he isn't interrupting a walk, and decides to finish the thought. They were prioritized.....to the point that they can't die, that the train saves them.....

But it's capable of pulling so many people. If it were just after a goal - is this specific combination of people that important? Why them, then? What can Ken and only Ken, this Ichijouji Ken, contribute to this train.....?

"Why would it....to that extent...."

"Ken-chan is smart," Wormmon informs Little Carrot. This fact is crucial. "He thinks lots of things I don't understand."