I am not a specialist in these questions concerning metallurgy, but it seems to me it refers more to centralized power, world trade, wars, politics and such -- not really quality of metal and art of smithing. What I heard from others is that inspite of the fact that wrought iron is produced from cast iron (extra stage compared to bloom process) it is more efficient for bigger scale production. One of the reasons is high level of personal knowledge needed to run bloomery process properly .With cast iron you can involve masses of less trained work force.
However I am completely sure about the fact that a thousand years ago bloomeries produced material of at least not worse quality than wrought iron and blister steel. Returning to my axes -- they need very high quality of iron, higher than 18 ct AD regular welded eye axe need. Any weak spot and they will split at one stage or another.. I often have to pre –weld modern mild steel to prevent this.