Well we need to make a bigger jump back in time. To the romans! The romans had an huge armor industry. After the fall of the west roman empire this industry ran out of orders. The big roman army in the west was gone. No one was there to buy armor. So over centuries the armor production declined. It didn’t vanish, we still have the corpus of finds from the early middle ages, where maille and scale armor, similar to the roman stuff was found. As well as helmets like the Sutton Hoo finds which are beautiful and highly decorated. This tells us, there still had to be smiths left that could produce armor of such high quality.
In vienna a helmet, about 500 p.Chr., might be from “Ravenna”, in northern Italy. We have little evidence but probably there armor was still produced. At later time, Genua, Milan etc. pp., which are also sited in northern Italy were to produce armor again in large quantities. Steel production has been there for centuries.
So, we have less armorers. Less customers as well and a change in military strategy. When Francia showed up a new military power existed in europe, which needed armor. So the production rose again. Have a look at this, the picture is taking from a bible of the 8th century. It shows us a fight David vs. Goliath, while about a hundred years later the soldiers are shown in scale armor.
If you now take a look at the Bayeux Tapestry the maille/scale armor reaches above the knees. While two centuries later the maille covers the whole body.
So yes, there was development. They had to create new patterns, for example how to cover the legs and be able to ride/walk/fight in it. And to rediscover old techniques.
The romans had waterpowered hammers, as the industry vanished those hammers did too. You can’t produce steel sheets in high numbers without such hammers. Without sheet --> No plate armor. Small scales are no problem to make. But helmets? No chance. The first one piece helmets in Europe since the roman empire were produced in the 11th century. And during the 12th century they start to make new helmet styles. (Great helm) In the 13th century knee cops show up. At the end the first coat of plates can be found. So yes, there was development.