The pilots can run away a lot easier than the company. Further investigation could uncover wrong doing on the company's part, tip of the iceberg stuff. Remember it was the US tax authorities that got Al Capone, not the police. The German tax office is staffed by people who would have passed the aptitude test for the gestapo with flying colours.
Threats to seize company assets and the possibility of prolonged legal action against an opponent who doesn't need to worry about the cost may cause MOL to reconsider his position.