Maybe the low-power feature of Bluetooth helped it, such as with the Bluetooth LE (Low Energy) spec that with the way "services" and "characteristics" are defined that it allows for extremely low power consumption when no read-operation is done and thus the Bluetooth radio power can be minimized. Also, the 2.4 GHz band of Bluetooth is inherently less power consuming than the higher frequency band of Wireless USB.
But I guess the other problems may have been due to as the OP article brings up about it being in a different frequency communication band. Bluetooth on the other hand shares the same frequency band as Wi-Fi (2.4 GHz (which is also the OG Wi-Fi frequency band)). Thus for PC and mobile device OEMs, it is one less antenna to integrate. Furthermore, the higher frequency of the band would have made through-walls and further-distance communication less reliable. In this context, one of the few cool applications of wireless USB would've been a wireless keyboard or mouse (but this is coming from someone who is working on an OEM computer keyboard and mouse).
But I guess the other problems may have been due to as the OP article brings up about it being in a different frequency communication band. Bluetooth on the other hand shares the same frequency band as Wi-Fi (2.4 GHz (which is also the OG Wi-Fi frequency band)). Thus for PC and mobile device OEMs, it is one less antenna to integrate. Furthermore, the higher frequency of the band would have made through-walls and further-distance communication less reliable. In this context, one of the few cool applications of wireless USB would've been a wireless keyboard or mouse (but this is coming from someone who is working on an OEM computer keyboard and mouse).