As an experienced and retired base jumper I can give some insight.
He setup a static line but misrouted his bridle through his lateral strap, the pins did extract and he got partial canopy inflation but this was not enough to save him. Nathan had around 120 BASE jumps and 5,500 skydives so he was an experienced jumper, but for some reason, maybe nerves at jumping from this location caused him to be careless in his setup and resulted in the fatal bridle miss-routing error.
Modern lightweight BASE canopies under a static line setup can be used from as low as 120feet depending on a few factors like the jumpers weight, canopy size/weight and jump altitude, so in this case a jump from 290 feet is not considered low in the sport of BASE jumping and is generally a pretty safe height ruling out external factors such as weather and lading hazards like power lines.
Other posters commenting on minimum safe altitude of 2,500 feet, this is for skydiving where a skydiving parachute is very different to a BASE jumping parachute. A BASE jumping parachute for a sub-terminal jump is packed with no slider, and a very large pilot chute up to 48", in Nathans case the bridle was tied to the building with 70lb rip cord in whats known as a static line, as he jumps and fall away from the building the static line pulls out his parachute to full line extension and then the 70lb cord breaks under tension and he should have been under a fully inflated canopy by arrox. 175 feet with plenty of time to fly his landing pattern and land safely. As mentioned in this case his bridle was wrapped around his harness lateral strap so the cord broke too early and was not able to fully extract his canopy.
Human error and nobody to give him a safety check resulted in this fatality, condolences to his family and friends and great luck that nobody else at the scene was injured by his carless jump.