Let's take as fact the claims that they are innocent and had no idea what they were doing because they are so sheltered etc. How on Earth did these kids parents let them travel abroad to Europe and Japan when that is the case? These kids don't speak or read English. They could not fill out the custom forms because they were in English. How could anyone expect them to function in a completely foreign country which has a very different culture? How did they expect to communicate with anyone in Japan for their most basic needs? I assume that they were planning to stay in Japan at least 1 night, how were they going to get from the airport to a hotel? Check in to the hotel? No one in Japan speaks Yiddish or Hebrew, they barely speak English. It is beyond me how any parent could allow a completely sheltered kid who has no understanding of the outside world abroad when they don't speak the language of the country or English. How were these kids supposed to communicate with anyone? Last I checked the universal translator has still not yet been invented.
No one would send an 8 year old to Japan by himself, yet, in essence that's what was done here. These bachurim in terms of worldly knowledge are probably not even the equivalent of an 8 year old. My 8 year old son (living in Israel) is more worldly then these kids. He speaks and read English and has been exposed to the outside world. He probably knows what drugs are. However, I would never dream of sending him by himself abroad.
You can't have it both ways. If you completely shelter your kids you cannot expect them to be able to deal with the outside world and travel around the world.