It spread because of France’s Alliance with Russia.
Not entirely. The stupidest human enterprise is shared to varying degrees by all parties.
There are some interesting if not different parallels often it’s something minor that sparks the wider conflict.
We better watch out because there is plenty going on is my point...
This
Bismarkian alliance juggling did not allow for the fragility of human ego reason and emotion being triggered by what should have been a minor diplomatic crisis into a deadly conflict between alliances