At a hospital in a Chicago suburb last winter, there were so few nurses that psychiatric patients with Covid were left waiting a full day for beds, and a single aide was on hand to assist with 32 infected patients. Nurses were so distraught about the inadequate staffing that they banded together to file formal complaints every day for more than a month.

About 300 miles away, at a hospital outside Flint, Mich., similar scenes were unfolding. Chronic understaffing meant that patients languished in dried feces, while robots replaced nursing assistants who would normally sit with mentally impaired patients.

Both hospitals are owned by one of the country’s largest health systems, Ascension. It spent years reducing its staffing levels in an effort to improve profitability, even though the chain is a nonprofit organization with nearly $18 billion of cash reserves.

Since the start of the pandemic, nurses have been leaving hospitals in droves. The exodus stems from many factors, with the hospital industry blaming Covid, staff burnout and tight labor markets for acute shortages of staff.

But a New York Times investigation has found that hospitals helped lay the groundwork for the labor crisis long before the arrival of the coronavirus. Looking to bolster their bottom lines, hospitals sought to wring more work out of fewer employees. When the pandemic swamped hospitals with critically ill patients, their lean staffing went from a financial strength to a glaring weakness.