where did it go wrong?

The Rise of the Catholic Church. Around 600CE-1000CE

The Catholic Church was surprisingly suppressive. Not of knowledge, or anything, but of any thought that would go against the Church's teachings.

Some Popes were lenient about it. But as time progressed, the church got corrupted from the amount of power it had.

The only problem, was that one entity held too much power, and was corrupted by it.

BUT, one could also go in this direction:

Nearing the end of the Roman Empire, the German Peoples were getting restless, and invaded Rome numerous times before causing the downfall of the Empire. AFTER WHICH they built their own Kingdoms.

And Unlike the Romans, they were interested mainly in garnering power, and keeping it. So they were at war constantly. And their of life didn't really dictate advanced though. They were modest (the poor ones that is). And they were working to survive. Not to create advanced thought.

These 2 things would go hand in hand though. As the Catholic Germans forged an Alliance with the Catholic Church and Dominated the Whole of Western, and Central Europe.

Don't be so sure. The states that followed were not strongly centralised, urban, bureaucratic & able to undertake massive public works or social organisation; however individual intelligence didn't nor did technology disappear.

If anything techology continued to advance but it's applications were more utilitarian & less historically eye catching that those of the classical world. Medieval Europe made far wider us of non-human power sources (water & wind) than Rome ever did, ferrous metal working techniques were able to produce greater quantities & higher quality goods and the diversity & general productivity of agriculture improved. The building of Europe's cathedrals required previously unheard of techniques & tolerances in the build; essentially taking stone to the limits of its structural potential & comfortable surpassing the height & complexity of building built until that time.

Also the people of the dark ages were far closer to us in ethical thinking & general mental outlook; our legal & social traditions come preponderantly from the Medieval period, we champion the individual & revile slavery & collective revenge, both of which were nigh-on social virtues in the classical world. It was their decentralised, individualistic society, that viewed techology as an asset not a potentially dangerous novelty that porogressed, in a fairly linear progression to Europe's global dominance.

Basically don't mistake a lightly organised & less widely literate society of small, relatively equal states for one that is less advanced, intellegent & virtuous than its monolithic forefathers.

I guess they call this the Dark Ages, where mankind lost its way for a while.