David Siegel spent more than four decades building Westgate Resorts into the largest privately held timeshare company in the world. Yet outside the hospitality industry, he became best known for a house that was supposed to celebrate his enormous success—and instead became an enduring symbol of ambition, excess, financial collapse, and an improbable comeback. In 2004, David and his wife, Jackie Siegel, began constructing a 90,000-square-foot pal…