Thanks for the hint regarding breakpoints.
This way I figured out that GameState::BeginPlay() happens after ActorComponent::BeginPlay() (after any component I surmise.
I used GameState::PreInitializeComponents instead of BeginPlay to set up my GameState according to my needs.
It makes me cry to see this forum in such a bad state. Your post is 7 years old and the reason why I routinely read these old posts: there simply isn’t any better documentation out there. I mean, wonderful how many developers put tutorials out there on youtube … but for troubleshooting, those videos just aren’t the right place and medium.