Do you think the bookies are stupid and haven't anticipated something like that?

They have their agents in the stands keeping an eye on the markets, closing and opening when needed based on what they see at the venues as well. If they aren't at the venue, they outsource this service to third-party companies who do it for them. If a match is played in a location where they can't find someone to monitor it, they will use the fastest TV channel/stream and do it from there. The delay is checked to make sure that live bettors don't have an unfair edge. That's why it takes up to 8 seconds for a live bet to be accepted when you try to place one.