[catherd]

Concrete foundations get stronger as the concrete cures (around a month).

Framing is much more resistant to collapse once you put sheathing on it, a roof, etc. Before that it is easier to fall over.

A half built wood frame wall only supported at one end is like a wet noodle if you don't put in some temporary braces.

[scarab92]

The concrete is supported by formwork and props until it cures, which appear to have been removed on all floors, suggesting that the concrete structure was now complete and the building is about as strong as it ever will be.

The collapse must have been due to a design or construction mistake.

[defrost]

There are a number of post concrete cured enhancements to buildings that improve earthquake resistance that may not yet have been added (if planned) .. antisway damping, additional bracing and or bridge like cabling, etc.