"why couldn't the pilot drive around the chopper?"
Reported that there was a brake failure and looking at the vid posted on Twitter the DHC-6 was going pretty fast at the collision point. Normally they would be at taxiing speed (i.e. controlled and able to stop or steer easily) well before that point. Suggests that the a/c was not in control therefore possibly due to a total brake failure or, more likely, right side brake failure (which would lead to a leftwards turn when the brakes were used). The a/c was so out of control it couldn't be kept on the paved runway let alone avoid obstacles! If this landing had been at, say Juliana and the pilot had detected a one-sided brake problem at touch down they could have either just let the a/c roll out using the rudder for directional control (runway is long enough and wide enough to do that) or taken off again (touch and go landing) and made another approach in which they planned a no brakes landing. Runway is too narrow & short at SBH for the former and landing on 28 (as in this case) the hill to the east west precludes the latter option (touch and go and go arounds prohibited on 28 at SBH).

"What the heck was the pilot doing?"
My guess is: the absolute best they could in a crisis. And there would have been two of them.

Again the safety margin for landings at SBH is small especially landing on 28.

Dave.

PS 28 Aug, can see both a/c on the ramp at SBH on the webcam, amazing that the left wing is so damaged on the DHC-6. Normal ops seem to have resumed.