It simply saw it as a long lens photo. They tend to compact a crowd but I wouldn't call it 'doctored'.
Yes, I would also say it was a telephoto lens, taken at a distance so it compacts the crowd. Also carefully cropped, so what I imagine are empty spaces to the right and left of a parade of people are removed, making the crowd seem larger. I would guess that there may have been a few thousand people, and that almost all of them are in that photo.
Given all the college leftists and useful idiots, and the money available to bus them in, it's not surprising that they could round up that many people.