Yes, I've just done some research and wiki says he later stated there'd been kidnap threats against members of his family. "Initially the reason given for missing the1978 World Cup were political reasons given a military dictatorship was in power in Argentina at that time. In 2008, however, Cruyff stated to the journalist Antoni Bassas in Catalunya Ràdio that he and his family were subject to a kidnap attempt in Barcelona a year before the tournament, and that this had caused his retirement. "To play a World Cup you have to be 200% okay, there are moments when there are other values in life." https://en.wikipedia.org/wiki/Johan_Cruyff#After_1974