I don’t think Gaza is irrelevant to the election, it’s just that it’s only an issue that a minority of people (some progressives, many Muslims, etc) care about to the extent that it’ll influence their voting pattern. So in a state election with a small margin between Harris and Trump, it could be one (of several) deciding factors as to who gets pushed over the edge. It’s like saying that the Libertarian Party or Green Party is totally irrelevant in the election just because neither will win outright - their mere presence will at least somewhat influence who will become the victor in swing states.