You raise a good point but that presupposes that we have a crowd estimate for the concert which we do not. But we do know that the band Obama’s campaign chose to precede him “often opens its own shows with the National Anthem of the now-defunct Soviet Union”. http://www.cnsnews.com/ViewCommentary.asp?Page=/Commentary/archive/200805/COM20080521e.html

Curious choice indeed but as we know, they are with the other side.

It’s not like the people left. I mean, Obama’s speech should’ve been interrupted by masses of uninterested people leaving then, right?

For all we know, they planned it like this on purpose.