Could well be concussion. Could also be the adrenalin wearing off and realising you've been riding on a busted ankle for 40k or whatever. I know when I hit the deck I'm usually up instantly and it's not until a bit later when I'm thinking "shit, maybe I should have a sit down.. ahh maybe later"
More on Vlasov, apparently vomiting towards the end of the stage.
https://www.stickybottle.com/races-results/vlasov-rode-final-50km-of-tour-gravel-stage-with-fractured-ankle-video/