The difference between fatalism and determinism seems to be the allowance for some kind of wiggle room as long as the wiggle room isn't considered free will.
What I'm seeing though is determinists, in their desire to avoid fatalism can't without allowing for some type of agent causality.
Determinism is not fatalism because...
Fatalism is the view that we are powerless to do anything other than what we actually do.
Causal determinism is "the idea that every event is necessitated by antecedent events and conditions together with the laws of nature".
So there's a cause for everything, but just because there is a necessary cause doesn't mean a necessary outcome.
Nomological determinism is the most common form of causal determinism. It is the notion that the past and the present dictate the future entirely and necessarily by rigid natural laws, that every occurrence results inevitably from prior events.
Determinism - Wikipedia
IOW any existent combination of causes have only one possible outcome.
Causal determinism seems to allow the necessary wiggle room.