A couple of quotes out of the NYT article for others to discuss
He inherited the works from his father, Hildebrand Gurlitt, an exuberant Nazi-era art dealer, partly Jewish, who at times worked in the service of the Third Reich but also counted artists disliked by the Nazis among his friends.
and
The collection was so valuable and, perhaps, its provenance so tainted by the family’s association with the Nazis, that the desire to keep it secure compelled Mr. Gurlitt to live a strange, Gollum-like existence behind permanently drawn blinds, obscuring not only the works but also the man himself.
and
Mr. Gurlitt told Der Spiegel that he knew a lot about the origins of the works but wanted to keep that information to himself, like a private love affair. “People only see banknotes between these papers with paint, unfortunately,” he said.