why does he go super ape shit as soon as there's people there to hold him back, was he waiting for an audience?
That's certainly a possibility.
Another is energy levels. His frustration was continually building, due the lack of response, but time was sapping his energy - he'd been flagging for the last minute or so. The presence of more people served to revive his energy and he stepped it up, although he faded fast again.
Yet another possibility is that he recognised that, with three men homing in on him, the game was just about over and the increase in aggression was a last ditch effort to "get his man".
A final possibility, the one that I thought of before I watched the video (in response to your question) is that sometimes a person wants to display aggression but not follow through.
While there was no-one there to constrain him, he made gestures (shouting, arm waving, carefully controlled kicks at the door) but did nothing definitively violent (door-bashing kicks, breaking the glass). When he went around to the front he didn't even bash the car's hood and on the passenger's side he made no attempt to use the gap in the window other than to make himself heard better, (although that could have been due to it being a female and/or not his prime target).
When the three men came along he was able to step up the
apparent aggression
safely, in the knowledge that he wouldn't be allowed - and therefore wouldn't have to commit - an actual act of violence.
Note that he didn't turn his anger on the other men, which was certainly an option. That has several possible reasons but the one that fits this story is that he wasn't actually looking for a fight.
If you're interested enough to watch the video again, do any of these narratives seem to fit?
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