Because the existential threats only exist because of political malfeasance. This has never been a technological problem: even the potentially disastrous consequences of climate change only really manifest because of - again - politics. Because governments won't spend to protect their own citizens, because of corruption and greed.
Little has changed on that front in thousands of years. Technology enabled almost everything we have now - even those improvements in governance we got (i.e. mass communications and the telegraph made coordinating large empires and alleviating local resource shortages via logistics possible).