I was at the course and heard them say 7500 people, but that was fairly early in the day. It definitely felt much more crowded for the senior races than the relay or U20s. So 10,000 people sounds like a believable number.
However, with the 2k loop, it was much better to stay inside the loop. There were at least one or two spectator crossovers, but those must've been closed for large parts of the race (keep in minds that the fields got spread out; people were getting lapped). So the main point to cross the course was the bridge by the roller coaster, and that got clogged up very easily. The best viewing spot, as mentioned earlier in this thread, was by the sand pit and water feature. You could watch the runners go through the sand, wait a minute, then see them come through the water. There was also a TV screen and speakers there to see the video coverage of the race.
All of this means there was basically no reason to be outside of the loop. And with the way the course was designed, the finish chute was left (to the inside), so there really wasn't a way to get spectators into that area to line both sides. It felt like a good atmosphere in person, but I can understand how that didn't translate to TV. It certainly felt more crowded and lively than even the HS state meets I've gone to.