There have always been a few evil sadistic men, but the frequency and severity of the atrocities seems to have increased,
both for individuals in our own country
and for whole movements in some other countries, e.g. rape and slavery returning as tools of war.
There is an Overton window in politics that defines the acceptable subset of political ideas.
Occasionally that gets dragged to the left or right - e.g. Attlee, Thatcher - and society changes dramatically within a decade
imo, the "Male Behaviour Window" seems to have been pushed massively to "Violent & Sadistic"
I suspect one cause is online pornography because that is a sudden social change, from tech innovation, that has never occurred before in human history
It is much more vivid than paper pictures or the written word
It can be used for hours in private, without social constraints
It stimulates the brain far more.
Particularly as some young men now will have started watching violent porn while they were still children
Some boys & men may be more vulnerable to its effects, just as some people can be far more easily adicted to alcohol, whereas others are mostly unaffected by its ready availability.