Causality (ie claiming effects have causes) is not identical to determinism (ie effects are uniquely defined by causes in one-to-one manner).
Causality can co-exist with indeterminism proper, at least in the sense that causes limit the set of possible outcomes and/or provide constraints which the possible outcomes must satisfy and provide a drive towards a set of possible outcomes. So, even though which outcome is finally realized is open, it is bound to be from this set of outcomes, circumscribed and driven by these causes.
Thus we can easily claim that effects have causes even though there might be indeterminacies involved.
Example: radioactive decay may be spontaneous, but atomic bombs do not blow up in our faces everyday. There have to be some prerequisites in place that guide spantaneous decay to create the bomb. These are the causes for the bomb, even though decay is spontaneous.
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Indeterminism, causality and information: Has physics ever been deterministic?
A tradition handed down among physicists maintains that classical
physics is a perfectly deterministic theory capable of predicting the
future with absolute certainty, independently of any interpretations.
It also tells that it was quantum mechanics that introduced
fundamental indeterminacy into physics. We show that there exist
alternative stories to be told in which classical mechanics, too, can
be interpreted as a fundamentally indeterministic theory. On the one
hand, this leaves room for the many possibilities of an open future,
yet, on the other, it brings into classical physics some of the
conceptual issues typical of quantum mechanics, such as the
measurement problem. We discuss here some of the issues of an
alternative, indeterministic classical physics and their relation to
the theory of information and the notion of causality.
P.S As you may read in above attachment, indeterminism provides the context for attaching meaning to causality, which in determinism is either trivial or non-existent alltogether.