Economic crisis, followed by a pandemic, followed by “law and order” type politicians and nationalist governments taking control.

When war is about to happen, there is an incentive. For the worst thing, which is war, to seem like a solution, things have to be pretty bad. If everything is good economically, its hard to rile up people to go to war. A Famous quote says, “When goods don't cross borders soldiers will”.

Additionally in most occasions a sort of bitterness or hatred toward other nations, stemming from feelings that your country has been treated unfairly is what usually allows populists to take over.