I think they believed that the terrain gave them enough of an advantage to negate the Soldiers' discipline and competence. Events seem to bear that out.

Another thought - the three attempts to reinforce the OP all ran directly to the OP itself. This appears to me to be the equivalent of rushing into the kill zone of a far ambush to reinforce the element in contact. From my couch in a well lit and air-conditioned room, with no one shooting at me, my first thought is to attack and seize key enemy positions, relieving pressure on the defenders at the OP, before seeking to move to the OP proper.

While talking with members of an ODA following an IED attack on my vehicle not far from Camp Blessing and the Waygal Valley, I mentioned that I immediately told the driver to keep going and get us out of the kill zone, even though I knew our gunner had been thrown from the turret. One of the team members thought it was screwed up that I was going to leave the gunner. I told him that it would have done the gunner no good to jump out of the vehicle and immediately get pinned down, if not get hit, in the kill zone. Far better to escape the kill zone and fight back to the casualty. As it was, the vehicle's engine was completely destroyed by the IED, and there was no accompanying ambush, so it was moot.

The gunner was fine, BTW. Just a few scalp lacerations.