Federal and local officials, housing experts, landlords and tenants cited an array of problems that slowed the flow of aid: bureaucratic missteps at all levels of government, onerous applications, resistance from landlords, the reluctance of local officials to ease eligibility requirements for the poor, difficulty raising awareness that rental aid even existed, and a steep rise in rents that increased the incentive for kicking out low-income tenants.

More than anything, the failure illustrates the difficulty of trying to build a vast new social program from scratch in under a year, and the inability of policymakers to fully anticipate the challenges of navigating a rental market dominated by mom-and-pop operators outside the more regulated world of owner-occupied housing.

“We asked state and local governments to do something they’d never done before,” said Vincent Reina, a professor of urban planning at the University of Pennsylvania who has studied pandemic aid programs. “They had to design large programs with complex systems in real time, then modify them in real time — and at the same time, we’re expecting these programs to resolve longstanding problems in the housing market.”