Why are there private Wi-Fi and managed networks on my iPhone?

All 3 are added by Verizon. It does not mean your phone is managed by Verizon or they have access to your data. The purpose is to enable WiFi features where Cellular service is congested or not available. Every cell carrier I know have has at least 1 managed Wifi Network that will appear there.

• A Managed Wi-Fi Network may be identified as "VerizonWiFi Passpoint," "VerizonWiFiAccess," or "PrivateMobileWiFi" when you connect. Once connected, your data connectivity will be supplied by the Managed Wi-Fi Network. If you have enabled Wi-Fi calling, your voice and text messages may be transmitted over the Managed Wi-Fi Network as well. We require these entities to limit data access, use and retention only to what is essential to provide the WiFi service.

https://www.verizon.com/support/important-plan-information/