SwiftUI update master list from detail view

Simple master screen with list, NavigationLink to editable detail view.

I want edits on the detail screen to update to the master list "cars" variable and the list UI.

1. On the detail view, if I edit one field and exit the field, the value reverts to the original value. Why?
2. If I edit one field, don't change focus and hit the back button. The master list updates. This is what I want, but I can only update 1 field because of problem #1. Should be able to edit all the fields.
3. If I implement the == func in the Car struct, then no updates get saved. Why?

struct Car: Hashable, Equatable {
    var id: UUID = UUID()
    var make: String
    var model: String
    var year: Int
    
//    static func == (lhs: Car, rhs: Car) -> Bool {
//        return lhs.id == rhs.id
//    }
}
 
struct ContentView: View {
    
    @State private var cars: [Car]
    
    init() {
        cars = [
            Car(make: "Toyota", model: "Camry", year: 2020),
            Car(make: "Honda", model: "Civic", year: 2021),
            Car(make: "Ford", model: "Mustang", year: 2022),
            Car(make: "Chevrolet", model: "Malibu", year: 2023),
            Car(make: "Nissan", model: "Altima", year: 2024),
            Car(make: "Kia", model: "Soul", year: 2025),
            Car(make: "Volkswagen", model: "Jetta", year: 2026)
        ]
    }
        
    var body: some View {
        NavigationStack {
            VStack {
                ForEach($cars, id: \.self) { $car in
                    NavigationLink(destination: CarDetailView(car: $car)){
                        Text(car.make)
                    }
                }
            }
        }
    }
}
 
struct CarDetailView: View {
    @Binding var car: Car
        
    var body: some View {
        Form {
            TextField("Make", text: $car.make)
            TextField("Model", text: $car.model)
            TextField("Year", value: $car.year, format: .number)
        }
    }
}