Bruno taught well into his early forties. What, then, led to his ‘leaving the world’, so to speak, and to founding the then and now strictest  order in  the Roman Catholic church? Very simply it seems to have been this. Bruno was named  chancellor of the diocese of Rheims in his early forties. The problem was that  the bishop had obtained his ‘see’ illegally by simony, a common enough practice at the time.  Denounced by his priests as not fit  for his episcopal office and consequent duties, he nonetheless succeeded in banishing them from his diocese rather than they him. Even the then quite able Cluniac Reform-minded Gregory VII, the Great was frustrated in his efforts to  remove him from his Office. 

So, given that difficult situation, Bruno returned  to Cologne, began to think of other ways of serving God, returned to Rheims briefly, where it is said rather than become a bishop himself, he gave  up all his worldly goods,  and with a few companions went to Molesmes, put himself under the tutelage of Robert of Molesmes, one of the three reform-minded founders of the Cistercians. But did not find enough solitude in the life of this  newly founded Cistercian order. So, he and a few of his devotees sought permission from a former pupil of his, the then bishop of Grenoble in Annecy, Hugh of Grenoble, to live on a  tract of land in his diocese and pursue there their
life of solitude and contemplation. The remote valley which these few men occupied was called La Chartreuse, which  later became La Grande Chartreuse and motherhouse of the Carthusian Order. 

Bruno was fifty when he entered this valley in 1084. He died in 1101 at 66 years  of age. He lived in a cave in Rome for a while in the service of Pope Urban II, that former pupil of his who called the first Crusade.