Because the problem is in the /system partition, which a factory reset does not touch. You need to reflash the ROM or manually replace the Account Manager APK.
. While its primary role is to sync Google services in the background, it has become widely known in tech communities as a key tool for bypassing Factory Reset Protection (FRP) The Role of Google Account Manager 6.0.1 System Synchronization android google account manager 601 link
Instead of searching for a "601 link," use trusted repositories: Because the problem is in the /system partition,
If you are trying to , could you tell me the model and Android version ? I can help find the most reliable method for that specific hardware. Manage your Google Settings - Google Account Help android google account manager 601 link