Why did roman knowledge, infrastructure and administration not locally survive after West Rome collapsed?
As far as I understand, when the Western Roman Empire collapsed, a lot of the achievements of Rome were forgotten. Roads were no longer maintained, culture collapsed, completely new and less sophisticated political structures emerged. And for 1000 years, Europe fell behind.
I ask myself: If there were still capable engineers, administrators etc. around, why did not small pockets of roman societies survive? Even if the capitol was gone and central structures disappeared, when I assume that roman societies were highly functional and working better than other societies at that point, why did they not form armies and create Rome-like smaller countries, that survived the centuries?
Were they disadvantaged e.g. militarily compared to the germanic peoples? Or could roman administration only work for larger countries, and smaller countries were more efficient when they had simple monarchies and tribe-like structures? Or was it like the collapse of the bronze age, that supply routes collapsed, and roman administrators were inefficient without paper? Or did everything happen just so fast that they could not adapt in time?