The city council aporoved minerals being removed from the water that prevented lead from leaching out of the pipes. They did so to save money. That’s what caused the problem in the first case.
Some inside baseball:
The Flint City Council had signed on with a new water project (at the promise of cheaper water) to replace Detroit as Flint’s water supplier.
Detroit then terminated the supply agreement with Flint.
Flint then re-activated their old treatment plant and didn’t remember (or ignored the fact) that their source (the Flint River) had a tendency to cause high Lead levels (requiring expensive treatment), which had resulted in the supply agreement with Detroit).