Several reasons. For one we've broken the climate and poisoned our habitat, this will for sure cause major problems for existing power structures. We're not sure when, just that it will, eventually. There will be massive amounts of refugees and unemployment, as well as strongly argued and broadly supported demands for accountability.
For another we've definitely decided to not put effort into international law and instead run with a might-makes-right kind of ethics in international relations. One sign that this was the case was the US repeatedly perpetrating the crime of aggression in the early 2000s, another was the ethnic cleansing of Nagorno Karabakh/Artsakh in 2023, as well as ongoing genocidal and similar campaigns in e.g. Sudan, DR Congo and likely the Caribbean and/or South America in the future. Ukraine is yet another example. Currently China is probably the last major country to heavily prioritise money and trade over atrocities and tribute.
Then there's the future of technology. Software has been treading water since the seventies while at the same time promising to deliver some utopian revolution anytime now. Sometimes it's promised to war machines, like GOFAI often was, sometimes it's promised to the general public, usually it doesn't deliver outside of making either legal conflict (i.e. commerce, political participation and the like) or illegal conflict (i.e. mafia, non-parliamentary/autonomous political participation, and the like) and the state response more efficient and intense.
Some in power expect computers to replace labour on a massive scale sometime soon, in part because that's a promise that has been made. Some also expect computerised fake persons and marketing-adjacent technologies to finally make democratic ambitions impossible to realise. It's also expected that people will have to be kept in their place for other, more mundane reasons.
Climate protests, anti-genocide protests and so on show that people are still willing to put themselves in harms way for some ethical purpose and hope for a decent future. This is very scary if you're a contemporary world leader, because there is this harsh disconnect between the stories you tell yourself and others in a similar position about what you do and how you're perceived by your constituents. Basically they think they're doing their best and that's admirable, and the rest of us think they're shit and deserve to be harshly punished.
There's also the spectre of history. Once upon a time ordinary people took a lot of power for themselves, and sometimes they just murdered their leaders. Dragged them out on a town square and chopped their heads off, or shot them or beat them with bamboo until they died. When the conditions look like it might be time for revolution and you're the one holding the levers of power you get scared. The might-makes-right-states are also scary, because those that haven't made the jump already don't have a bloc that backs them up, unlike the socialist states and the capitalist ones and the third world collective did way back when.
So, we're in a hurry to figure out how to make sure local populations cannot revolt, and next up is to figure out whether there are actually any allies or whether this is a war of all against all.