With that phone call, Mr. Diller ended a six-year saga that had cost $40 million before construction had started in earnest. The pier had grown from a relatively modest original proposal into a grand project worthy of a billionaire’s ambitions. It was stalled in the courts by a tiny band of activists backed by an opposing billionaire, Douglas Durst of the New York real estate family. And it was a battle as much about shifting personal relationships and hurt feelings as it was about city or state regulations or the delicate environment of the Hudson River estuary.

Its denouement demonstrates some of the dangers of turning over funding of city infrastructure to individuals with deep pockets but, perhaps, thinner skins.

“Diller joined David Rockefeller in being another billionaire who couldn’t impose his will on the West Side waterfront,” said Mitchell Moss, a professor of urban planning at New York University, recalling Mr. Rockefeller’s backing of the failed Westway highway project. “Hudson River Park emerged from the failure of Westway. There will be new ideas that emerge from the failure of Diller Island.”

Indeed, the Hudson River waterfront has long been contested territory. Westway, a multibillion dollar plan to build a six-lane highway along the river with hundreds of acres of concrete platforms and residential towers, was defeated in 1985 , after environmental activists sued, saying the project would endanger the striped bass in the river.

After Westway’s demise, the state and city in 1992 agreed to fund the establishment of the park, but in a controversial move, they said that money for its maintenance would come from commercial development along the waterfront. It would be overseen by the Hudson River Park Trust, a public benefit corporation.

Ms. Wils who joined the Trust in 2011, said that the government had agreed to build the park, which runs from Battery Park City to West 59th Street along Manhattan’s edge, and poured about $550 million into its creation. But it still needs another $200 million to be complete. Absent additional money from the state or the city, the Trust has long had to scrounge for funds.

Not long after taking over at the Trust, Ms. Wils, along with Diana L. Taylor, the chairwoman of the Trust’s board of directors and the longtime companion of former Mayor Michael R. Bloomberg, approached Mr. Diller about rebuilding Pier 54, a narrow finger pier where the Trust held concerts and other gatherings, that was slowly sinking into the river. Their plan was to replace it with an amoeba-shaped structure with a loosely estimated $35 million price tag.