What happened in 476 AD? Not much, if you look into the history.
By tradition, 476 AD marks the end of the Roman Empire and the end of antiquity: the latter transitioning to the Middle Ages, at least in Europe. I say “so what” because there is no catastrophic ending to the empire that year, only the minor event of the deposition of the last Roman Emperor Romulus Augutulus.
Romulus, aged fourteen, was proclaimed emperor on October 31st, 475 AD by his father Orestes, who was master of soldiers of the Roman army. He followed Julius Nepos, who had reigned for one year before being deposed and forced to flee by ship when Orestes took control of the Roman capital at Ravenna. Romulus was a figurehead covering the rule of his father and his status as emperor was disputed outside of central Italy from the outset. Ten months after his reign began, Romulus was deposed by Odoacer who invaded Italy, defeating and killing Orestes. Odoacer proclaimed himself King of Italy and not emperor of the west, ending the traditional line of emperors. Despite the change in title, Odoacer had the support of the Senate, so Rome (or more accurately) Italy had a king for the first time in nearly a thousand years.
What is there about the Empire in 476 that inspires me to use the term "minor event" to describe a change in rulers?
First of all, the span of control exerted by the western empire had shrunk down to Italy and parts of southern France by the mid-400s - hardly what we would call an empire. The emperor of the east had been an independent operator after 395 AD, so the western emperor had no say in the Balkans and points east. The Visigoths controlled Spain and shared southwestern Gaul with the Burgundians while the Franks controlled the north of Gaul. Africa was under the influence of the Vandals who had successfully attacked Carthage in 439 AD.
Second, Attila the Hun terrorized Gaul and the Italian peninsula between 440 and 451, so even the territory the empire controlled was ravaged. In 456 AD, Gaiseric the Vandal landed at Ostia and spent two weeks plundering Rome, after which he exited with thousands of captives. The imperial geography was not under control and was subject to attacks at any time. The word empire implies power and the western emperor had none.
Third, Rome was no longer the imperial capital, having ceded that role to Ravenna in 402 AD. You might even want to say that Ravenna was the fortress that protected the imperial court rather than the capital, because it didn’t represent the center of government. It was only chosen only because it was easier than Rome to defend. When the Visigoths sacked Rome in 410 AD, they bypassed Ravenna because they figured (correctly) there was still enough left in Rome to plunder, and the swamps of Ravenna were not worth wading through.
The Senate was still in operation during this time and was propped up by Odoacer and subsequent Barbarian leaders who sought to protect it by making the leader of the Senate a key adviser to the king. The Senate was actually able to wield occasional power, as in the case of installing Laurentius as pope in 498 against the emperor’s wishes. Later in 552, many Senators were taken hostage and some were executed during a war between the Ostogothic king Theodahad and the eastern emperor Justinian. The latter eventually banned all Senatorial offices in Italy.
So we see that in the year 476 AD, the western empire controlled a small amount of territory without the means to govern or protect it. The western emperor had virtually no power absent the support of the army. The great institutions we think of as Rome – the monuments, the great army, the well-oiled political system, and the engineering – were all gone, so one last weak emperor’s deposition is hardly worth the headline.
It was the barbarians who held power over Rome and would eventually destroy it. Ironically, they would rather have had a strong and stable Rome as a partner, but the inner strength of the empire was gone and Rome did not have the capacity to continue. All that the Romans had accomplished during their thousand years was lost. Europe had to start over; re-inventing governments, laws, and new cultures.