Winners win! Those who look like winners tend to end up as winners. And that is why this poll is significant. It shows the SNP as winners. The specifics don't matter so much as the overall impression. They don't have to actually win anything. So long as they look like winners.
The thing the British establishment feared most; the thing they'd been assured would not follow from devolution, was happening. The SNP was in power. What was worse, they were doing a good job.