HONG KONG—For six years, Chinese billionaire Jia Yueting shrugged off skeptics as he pursued his vision of a business that Inc. all at once.

The founder of LeEco Holdings appeared to defy gravity as he built a second-tier video site into a conglomerate spanning smartphones, TVs, electric cars, cloud computing and a film studio, capped off in August by a $2 billion deal to buy U.S. TV maker Vizio Inc.

But...