During the past quarter century, more than a dozen New York City hospitals have closed. The causes of death have been many: changing economics, deregulation, less government support, a shift toward more outpatient treatment.

It seemed likely that University Hospital at Downstate in East Flatbush, Brooklyn, would soon join that casualty list, especially when state officials began formulating a plan last year for the hospital’s demise. After all, the medical center, part of SUNY Downstate Health Sciences University, had hemorrhaged money and patients for years. A far larger hospital sits directly across the street, ensuring that the neighborhood — plagued with high rates of diabetes, hypertension and kidney disease — would not be without medical care.

But then something unexpected happened. The state decided to commit $1.1 billion to University Hospital for renovations and a new outpatient facility, a stunning reversal propelled by fervent local opposition to the closing of the 342-bed hospital.

When the hospital’s future was in doubt, state legislators and community activists demanded that the state find the money to keep it open. Pastors spoke about it in their Sunday sermons. Rallies to save the hospital drew speakers including the Rev. Al Sharpton and Randi Weingarten, the president of the American Federation of Teachers, a major union.

And patients mobilized to save their hospital, even though the federal government gives it only one star out of five in its quality rating. By the end, the administration of Gov. Kathy Hochul enthusiastically came around to the idea of shoring up the hospital instead of shutting it down.

“Let’s say that again, it sounds so good: $1 billion,” Ms. Hochul, a Democrat, said at a news conference this month at SUNY Downstate, announcing the sum that the state was providing for improvements. The money is expected to go toward renovating the hospital and expanding cancer and cardiac care.