How does Kim Yong-il - who secludes North Korea from the world - allow for a national football team to participate in the FIFA World Cup?

Answer 1

Simple: Propaganda and publicity.

Even showing up at such a tournament, let alone winning matches or advancing beyond preliminary rounds, demonstrates ability and strength on behalf of that nation. Monetary profit is also made from advertising, televising matches, merchandise and the many other offshoot effects from such an event.