Why does a root-cause report list more than one possible cause?

Because the report lists every cause the investigation can actually support with evidence, not a single guess picked to look decisive. RCA works from the case’s trace evidence and, when one is connected, your repo, testing explanations against what actually happened, and more than one can hold up: a real regression sometimes has more than one contributing change. Alongside the hypotheses it keeps, the report lists what it checked and ruled out, so an engineer reading it doesn’t waste time re-testing an explanation RCA already closed off. Where exactly one hypothesis is grounded enough to act on, the report points to it directly; when more than one plausible cause survives, you’re the one who decides which explanation to build on. The report exists to shorten the investigation you’d otherwise start from scratch, not to replace your judgment on it.