Theyve always been there. Every military in the world is an attractive spot for these people.
I think this is a pretty commonly held misconception about the nature of genocide or crimes against humanity. We all have the potential to partake in such actions, the vast majority of people who partake in these crimes are just every day normal people.
The Russian military creates misery wherever they go because being in the Russian military has been a miserable state of existence for the last three hundred years.
No matter what government or time and place in history, being enlisted or conscripted in the Russian military has meant that you will be hazed, raped, stolen from, and then made to rape, steal, and haze new recruits. It’s an actual part of how they maintain institutional discipline.