A member of the aristocratic von Steusslingen family, Anno embarked on a military career but his uncle persuaded him to serve the Church instead. As was frequently the case with eleventh century aristocrats joining the ecclesiastical ranks, Anno rose quickly. Becoming the Confessor to Emperor Henry III was an especially lucky career break, leading to his appointment as Bishop of Cologne. One of the ancillary but important duties of that office was serving as Chancellor of Italy (since Italy was theoretically one kingdom and also theoretically under the Holy Roman Emperor).
When young Henry IV was crowned King of the Germans at the tender age of six, his mom Agnes served as his regent. Anno, who served as his tutor, conspired with some nobles to take control of the regency, but he in turn was bumped by Adalbert, the bishop of Bremen. Adalbert brought some unscrupulous types with him, making even the King long for the strict regimen of Anno.
The underhanded double-dealing of princes and popes in the eleventh century has filled volumes. I don't want to go into it much here, except to say that Anno was up to his ears in it all. I get the impression he was one of the few straight arrows in the whole crooked quiver. Perhaps the deals he cut and horses he backed were part of the reason he spent his final years in semi-retirement at the Michaelsburg Abbey, penitently praying. Well, that plus his sponsorship of his nephew Cunon (remember that his uncle had sponsored his Church career) had gotten the young lad murdered by an ugly count named Theodoric. That would be a tough thing to swallow at the end of a long, contentious career.