1) it's easier to imagine the end of the world than the end of the current system;

2) the current system is ending, soon. it is not sustainable, socially, politically, environmentally;

3) our dispreference for the end of the world (nuclear war) diminishes — our willingness to take risks with collective survival increases — as something similarly scary seems already baked in, a sunk cost. the end of the world seems less worse-than-the-alternatives than it used to seem.