Two thoughts come to mind when looking at that result.
First, how electoral reform shows that there is scope for cross-party cooperation, or even realignment, beyond simply a reaction to the European referendum.
Second, how weak the grassroots campaign infrastructure is in favour of electoral reform. I know several people who work for organisations that support PR and they and their colleagues are certainly hard-working, but it is fair to also point out how small scale such efforts are. There is no mass-membership organisation regularly pushing for electoral and other political reform. Hence the relatively low key efforts to mobilise public support ahead of the vote.