I have a simple SwiftUI view like this, where the animation is performed correctly:

struct DemoView: View {
    @State private var isAnimating = false
    
    var body: some View {
        Text("Hello")
            .rotationEffect(.degrees(isAnimating ? 360 : 0))
            .animation(.smooth.repeatForever(), value: isAnimating)
            .onAppear(perform: {
                isAnimating = true
            })
    }
}

But as soon as I wrapped its content or embedded it into a TabView the animation stop working (not performed):

struct DemoView: View {
    @State private var isAnimating = false
    
    var body: some View {
        TabView {
            Text("Hello")
                .rotationEffect(.degrees(isAnimating ? 360 : 0))
                .animation(.smooth.repeatForever(), value: isAnimating)
                .onAppear(perform: {
                    isAnimating = true
                })
        }
    }
}

Note: I’m testing this on a WatchOS project.