Some information released from the Time Control archives:
The Dark Ages
Though a very inaccurate appellation, the term Dark Ages does describe poetically the lack of technological progresss by Man in that period. Well, that was quite a deliberate act on our part. The forecasts showed a true spacefaring civilisation by the 1820s if we had not stepped in. Such a result would have ruined the required outcome for Earth and its "unsaved".
Though this was perhaps our largest intervention, it was still quite a simple plan. Essentially, the agents merely injected more religious faith into the meme ecosystem. Such a factor has always had a retarding effect on society and so it was with Earth too.
Wolfgang Amadeus Mozart
Very few humans have the same intellect as ourselves, but when they appear in the time stream, we deal with them as otherwise their effect on human development would not be to our advantage. Mozart had been calculated to have been capable of advancing human progress by at least 200 years, so he was selected for an intervention.
We of course do not remove these people from the stream, as has been attempted in the "past", but we do move them. Official records indicate that Mozart was originally born in 1233, a time when he would have had catastrophic effect on our attempts to slow human progress. We merely moved him to 1756 and encouraged his father to nurture his music abilities. If Mozart had been allowed to develop in the sciences, even as late as 1756, it would have not been to our advantage.