Complex sentence: In 1810 he became stranded in Boston by the loss of his entire fortune in the Napoleonic wars and ensuing economic crash, and resolved to fall back on his long-time avocation and become a professional violinist and conductor.
Split into simpler sentences: In 1810 he became stranded in Boston by the loss of his entire fortune in the Napoleonic wars and ensuing economic crash. Penniless, he resolved to fall back on his long-time avocation and become a professional violinist and conductor.