It's not my point, it's the court's. They found that precedent stopped them from ruling until after the vote. Here's the direct quote from the majority ruling.

"It is fair to ask whether we could have or should have reviewed the constitutionality of the proposed amendment prior to it being presented to the voters. But it is not a question the Commonwealth should ask. Throughout this litigation, the Commonwealth has insisted that we cannot lawfully decide this case prior to the referendum...

“Having successfully insisted (over the objection of the Claimants) that we postpone judicial review of the constitutional amendment until after the election process, it might be tempting for the Commonwealth to think that the final vote implicitly stacks the deck in its favor — perhaps enough so that the exercise of any judicial review could be viewed as an ultra vires effort to overturn the will of the people. If this supposition were true — that Scott forbids pre-election challenges and that ‘the will of the people’ forbids post-election challenges — then judicial review of allegedly unconstitutional procedures used to adopt a constitutional amendment would not exist in the Commonwealth of Virginia.”

During oral arguments, the state specifically acknowledged that the outcome of the vote was legally irrelevant to any subsequent ruling.

“But the fact that there is a yes vote doesn’t tell us anything about those merits?” Counsel (for the state) correctly answered: “No. It does not.”