This is my job. Structural engineering. Simplified, the load exceeded the capacity. It’s likely this is in a high rise building or parking structure where loads are in the millions of pounds. Without further info it’s hard to tell. Could be an error in design, poor materials (concrete/steel), underestimated load, or poor construction. Usually structural failures are a combination of multiple factors, as there are safety factors to lesson the chance one error leads to catastrophe.
Concrete never has negative capacity (whatever that is), to whoever said that. It does have low tensile strength, hence the addition of steel which has great tensile strength. Concrete’s best property is compressive strength. Not even close to steel’s but less expensive and easy to mold to the desired shape.
Column design is more complicated than pure cross section area times per inch compressive strength capacity. Buckling (think yard-stick used as column) where the column bends out of vertical plane, and compression “bulging” or the squashed marshmallow effect both limit design and often control the design.
Bottom line, lots of possible variables here and without further info we are all guessing.
