Seriously? XD Okay then!
The late Western Roman Empire was having a SERIOUS CRISIS. I'm talking, like, a century of chaotic warfare and invading barbarians and rogue legions declaring a new Emperor every five minutes. I'm not kidding - they went through 26 emperors in something like 50 years. It was a MESS. And of course, not only was it immensely damaging for the structure of the empire, it was also stupidly expensive, because everyone had to keep bribing each other to stave of assassination.
So when Emperor Diocletian finally rose to power and the whole ridiculous crisis ended, he decided to clean house and do some serious reorganising. So he did. Not only did he increase the number of imperial officials, he also reorganised the administrative structure of the empire. He created more administrative regions, grouped them together in diocese, and gave the people in charge of these regions more power - not just the right to collect taxes, but to dispense justice, and to be in charge of the military as well.
This meant that even as Diocletian himself was kind of an absolutist - he was the one true ruler of the Empire, no pretending he was "of the people" like previous rulers - it effectively decentralised his power, and broke the Empire up into smaller, self-contained parts. He also reformed the tax-system, going from payment in coins to payment in kind - if you were a pig farmer, you could pay your taxes in pigs or pork. If you were a weaver, you could pay your taxes in bolts of cloth - meaning that those higher up the ladder were entitled not just to a share of your income, but to a share of your actual goods.
And finally, he made sure that peasants were tied to the land they farmed, and that people in various trades - bakers, cobblers, candlemakers, etc., - had their positions made hereditary, instituting an early form of the later medieval guild system and restraining people's upward social mobility.
So, in short, when the Western Roman Empire fell, it already had a bunch of pre-established administrative regions which were taken over by a.) the church (the Catholic church still refers to its various regions as "diocese") and b.) secular rulers, who could just turn around and declare themselves princes or kings of whatever power structure they were sitting at the top of. The payment-in-kind form of taxation became entrenched as well, and medieval princes could take their brand new goods and sell them to other princedoms, or keep them as they saw fit. And the guild-system was fairly strong in medieval Europe, leading to a social stability, even if it sometimes created stagnant economies.
And that, in a nutshell and shipping a lot of the details, is how a Roman Emperor accidentally caused feudalism. Mind you, "feudalism" is a debated concept, and not all historians like it.
.... You can have your thread back now. >.>
