Oh! I think @Drawkward has it in a way. At night, everyone leaves and basically goes straight home I think. I’ve been stuck in the directly after game traffic then and was in a perfect standstill for an hour.
During the afternoon, people mill about more, getting drunk or leaving early or whatever. So the traffic isn’t quite so bad. It takes about 20 minutes to get past the stadium, but the bus isn’t literally just sitting for an hour.