Yeah, if you start watching at 8:15:00 (holy shit, that's a massive video full of boring shit) it's pretty clear there's a lot of stuff going on around them, including behind them. He even gives a thumbs up before the wandering off. So there was something he was attracted to back there. It's possible he didn't realize that they were about to get spoken to because they were just standing there for a while already without anyone talking to them. I kinda don't blame him for wandering off and doing his own thing with so much going on and no one engaging them.

That being said, his facial expression and slowness still look like shit.