North Korea ”publicly executes” 30 middle school students... What's the reason? = South Korea

It has been revealed that North Korea has carried out a large-scale public execution of over 30 middle school students. A South Korean private organization picked up a USB inside a bag attached to a balloon sent to North Korea, and the USB
According to a report by the South Korean cable TV station TV Chosun on the 11th, North Korean authorities arrested more than 30 middle school students who had watched a South Korean TV series last week.
Last month, North Korea sentenced more than 30 teenagers around the age of 17 to life imprisonment or death for the same reasons.
In addition, a plastic bottle filled with rice sent by a South Korean anti-North Korean group afloat in the sea.
Residents who picked up the garbage, cooked it, and ate it were sentenced to "labor reform." North Korean authorities are currently imposing sanctions in accordance with the "Act on the Elimination of Reactionary Ideology and Culture" enacted in December 2020.
The law stipulates that "those who distribute Korean videos will be sentenced to death, and viewers will be subject to up to 15 years in prison."
In addition, books, songs, and photographs were also subject to punishment, and "South Korean language and singing style" was
There is also a clause that states, "For example, the offender shall be sentenced to two years of labor reform (imprisonment)."