The group that carried out the attack now fears exposure.
Source: This Washington Post Article.
Quote:
"The raid was initially a mystery, but the culprit was soon revealed: Free Joseon, an organization that calls for the overthrow of Kim's dynasty and had emerged publicly after the killing of the North Korean ruler's estranged half brother in 2017. The covert group was behind the act of defiance against the North Korean government. But as details of the raid became publicly known over the past few days, the group has pushed back against media attention, apparently fearful not only of the Spanish legal system but also the potential to be targeted by North Korea. Other activists and human rights groups are expressing concern that they, too, could face retaliation and other difficulties because of the raid."