(I’m not sure when the biography was written however the writer lived from 840-912ce)
I had to read his biography of Charlemagne for class last year and this has been bothering me ever since. He continually describes corruption within the Catholic Church including non-celibate bishops, lying monks, etc. Seeing how the Catholic Church cracked down on others who criticized it, why did this text survive? Since I’ve only read the biography and I haven’t done much research on the author himself I may be missing some information, but the book did not mention any negative repercussions from its creation.
Another question I would have going with this topic is how did the Catholic Church decide what works were heretical and needed to be destroyed during the middle ages?
Ok, so there are actually a few different questions buried in here, so let's deal with them one by one:
Firstly, the case of Notker himself. He was a monk at the royal abbey of St Gall in what is now Switzerland. He was writing a broadly complimentary work about Charlemagne, already by the 880s (when the work was probably written) regarded as almost legendary. His work was probably written for, and was certainly connected with the court, of Charles the Fat, the reigning emperor and Charlemagne's great-grandson. As long as he's not bad-mouthing the king or the royal family itself, he can write pretty much whatever he wants and no-one's going to do anything about it.
The idea of criticism of the Church being somehow taboo or something which wasn't done in the middle ages is completely anachronistic. While the Catholic church has in recent decades placed a premium of preserving it's reputation and position in society, this is a (relatively) recent phenomenon. Criticism of the church is pretty much constant throughout the medieval period, from local priests and priors all the way up to the papacy. Most of this criticism of the church is coming from the inside - monks (like Notker) are pretty notorious for constantly bitching about the lax standards of the secular clergy (I.e. non-monks). Admonitio, admonition or loving discipline, was a cornerstone of Carolingian, and medieval, religious thought; a king/bishop/pope/priest etc. was obligated to chastise and criticise those he saw sinning in order to bring them back to God and to save their souls. The entire religious history of the middle ages can probably be summed up as 'the church is immoral, corrupt and sinful - he's how you should really do it' repeated ad infinitum (until Martin Luther decides to change the game).
Finally, it's worth taking a second to dismantle the idea that the church was keen to destroy or erase ideas it disagreed with. That wasn't the case at all and, in many cases, our best knowledge about medieval heresies comes not from heretical texts themselves (heresies were often marginal and rarely had the resources to produce large numbers of manuscripts, let alone the infrastructure to preserve them), but from the writings of church leaders, preachers and inquisitors, who often record heretical beliefs in.great detail, in order to dismantle them and prove them wrong. Obviously, there's big methodological problems when working with these texts as a result, but the point is that the idea that the medieval church was actively working to destroy or conceal information which criticised it or which contradicted its teachings simply doesn't reflect the historical reality.