“This looks like the end,” one boy shouted into a smartphone, before another cut in: “Mom, Dad, I love you.”

Reinventing a Swindler

Such scenes reverberated around the world. Since then, scores of people have been arrested in connection with the sinking, including regulators, the captain, officers and members of the crew. But at the heart of the tragedy, and the investigation into how it happened, sits one of the nation’s most eccentric, and now reviled, families.

“The Yoo Byung-eun family, which is the root cause of this calamity, is inviting the ire of the people by flouting the law rather than repenting before the people and helping reveal the truth,” said President Park Geun-hye, who has also been widely criticized for her government’s failure to prevent the disaster, much less find Mr. Yoo before his death. His wife and two of his four children are now in custody, and one son remains at large.

Image The search for Mr. Yoo was the largest manhunt in South Korean history. Credit... Ahn Young-Joon/Associated Press

The Yoo family’s representatives did not provide answers to questions about the disaster, their businesses or their church. Many church members have said, however, that Ms. Park is trying to demonize the Yoos to deflect criticism from her government. But dozens of interviews with regulators, Coast Guard officials, prosecutors, dockworkers, crew members and family business associates seem to confirm the prosecutors’ contention that the Yoo family played a crucial role in the tragedy by cutting corners on the ferry’s safety, even as it was spending lavishly on itself.

The family used a sprawling group of at least 70 companies on three continents as a personal A.T.M., prosecutors say. In their own names or through companies that they control, family members own at least $8 million worth of real estate in the United States alone, including a condominium at the Ritz Carlton in Manhattan, and have the rights to be an American distributor of Debauve & Gallais, the French maker of luxury chocolates once favored by Marie Antoinette. In France, they own an entire hilltop village.

The family also spent tens of millions of dollars to lionize Mr. Yoo, a convicted swindler known best in South Korea in connection with the mass suicide of 32 members of a splinter group of his church more than two decades ago.