That Many Humans

There's a vast difference between our ancient ancestors who grew up in far, far harsher conditions and hence were far more adapted to the wild attacking a big, ponderous animal compared to a bunch of modern humans with no real experience in raw survival and no idea they were heading into a dangerous situation facing a similar sized creature that's faster, stronger, knows the territory, and has nasty natural weapons.

Also, a perfect situation to neutralize our natural advantages: our intelligence and ability to use tools. Nothing like stark fear to break brains.