After determining key factors for one observation, go back and repeat the process for the other observations. Continue until you have explained all the observations to ensure you haven't overlooked some key factors.
In the Fuse case, finding the key factors of one observation explained the other three.
The fuse which failed and caused the 'Pop' was in the motor control centre that was being started.
When it failed, it took out several other fuses, interrupting power to the four drives.
When the drives lost power, the motors they were controlling stopped, which caused the faceplate rolls that the motors were turning to also stop.
PHYSICAL FACTOR: Too small a fuse was installed in an application, which resulted in the fuse blowing apart catastrophically. The explosion took out many other fuses in a domino effect, which left many functions inoperable.
HUMAN FACTOR: Did not know proper fuse rating. Fuse rating label not read.
