Lead piping can be replaced slowly if there is no contact with the water. ie - if a mineral layer has thoroughly coated the inside of the pipes. That's how it was in Flint before hand.
An emergency manager switched to a different water supply - one that was more acidic. They could have treated the water to lower the pH and everything still would have been OK. But that would require steady purchases of chemicals, and ... (psst) they were saving money. (/psst)
Over about a year, the more acidic water leached through the mineral buildup. Started exposing the lead, and leaching that too. Lead readings started appearing erratically, then more and more consistently. Emergency manager and his boys concealed the readings, and downplayed the risks when people asked. Until someone told the EPA, and the house of cards collapsed. Those turkeys need jail time so bad.