There was an editorial piece on Byline Times recently, saying something similar - that Putin has stirred up ‘culture wars’ to destabilise the west and weaken leadership and alliances.
I do think that Cummings was responsible for segmenting groups (Boomers v Millennials, Metropolitan elite v The Rest, etc), the better to pick us all off, but in no case have the groups involved been to blame for any of it.
We all like to think that we are capable of autonomous thought, and sneering at the so-called MSM is usually a sign of the worst offenders, but the truth is that we are all manipulated all the time in more ways than we realise.