Same response I gave the other guy - you can go look up the market here rather than conjecturing [1]. It was about 25% the day before. In any case, it seems very silly to discount prediction markets because the probability didn't work the way you expected it to in a single event. The whole point of probability is that it's probabilistic!

[1]: https://www.predictit.org/markets/detail/1413/Will-the-UK-vo...