After the apartment block came down, one question has dominated: why did this building collapse? As the background of the disaster is peeled back, a chain of negligence is coming to light piece by piece. The architect who designed the building and the site supervisor overseeing its construction are both in custody. Early assessments focus on load-bearing columns that wore down over the years and could no longer take the weight of extra storeys added on top. Attention has also turned to the commercial premises at the entrance level, a spot where shops often mean walls cut into or doors widened. Investigators now face the task of tracing exactly who signed off on the alterations. Experts caution that the column fatigue theory still needs confirmation through detailed structural analysis.