Both human density and technology are to blame. If you have ever seen the result of over packing a cage of rats the effect is frightening. The hostility and violence goes murderous after a certain degree of density. People no less than rats need a certain minimum amount of space to function normally.
Now add, to the billions of folks who suddenly stress the planet for room and resources, the ability to amplify hostility through social media, we humans are starting to act like too many rats in a confined space. In the old days wars helped relive the stress, as bad as that was, but now with civilization ending nuclear weapons on hair trigger alert only small, mostly local or proxy wars dare be initiated. So the rhetoric is white hot in the place of outright war.