Complex sentence: His first hit, "It's Tulip Time in Holland" sold more than one million copies in just a few months in 1915 though because he sold it outright, he never received any royalties.
Split into simpler sentences: His first hit, "It's Tulip Time in Holland" sold more than one million copies in just a few months in 1915. Because he sold it outright, he never received any royalties.