Why did the Justice Department order the charges against New York City Mayor Eric Adams to be dropped?

According to Rachel Maddow's reporting, Donald Trump's Justice Department ordered federal prosecutors at the Southern District of New York (SDNY) to drop their case against Mayor Eric Adams, not due to any new exonerating evidence, but because Trump appointees at Main Justice claimed Adams was the victim of political persecution. Notably, the charges were ordered to be dismissed 'without prejudice,' a legal term meaning they could potentially be brought back at a later time. The memo specified that the charges 'shall be reviewed by the confirmed U.S.' leadership, suggesting this decision might be temporary. This has prompted resignations within the SDNY in protest against what appears to be political manipulation of the justice system.