Why Liberty ships and T2 tankers suffered brittle fractures

Why did Liberty ships and T2 tankers suffer so many brittle fractures?

Their rapid construction and the materials used in the emergency building program made brittle failure more likely.

The panel gives two causes for the brittle fractures: rapid emergency construction and the materials selected for the mass-produced hulls. It does not develop a detailed metallurgical explanation because another question interrupts the reply. The safe takeaway is that construction speed and material choice were connected to the failures. This brief passage does not support a more specific claim about individual crack mechanisms or fabrication defects.