At first glance it looked like the subject line read "Was Charlemagne an indulterer?" and I thought, what, weird, oh no here we go again...

Seriously though. The Old Testament on its own wouldn't seem to bode well, but God knows exactly what He's doing. The pagan, corrupt, and finally decaying Roman Empire is what became the vector for the spread of Christianity. Same with the Holy Roman Emperors, some of whom may not have been that holy personally.
Ponder less about what Charlemagne was up to in his spare time and instead stand back and gaze thankfully upon the vastness and wisdom of Divine Providence. And skip 99% of those fast media "sources" that only plant seeds of confusion and doubt.