Complex sentence: The Marquis wanted the castle kept as a living document of Swedish history, and after he died in 1930, he left Tyresö Palace to a museum foundation, the Nordic Museum (Swedish: "Nordiska museet").
Split into simpler sentences: The Marquis wanted the castle kept as a living document of Swedish history. The marquis died in 1930, and in his will left Tyresö Palace to a museum foundation, the Nordic Museum (Swedish: "Nordiska museet").