I think this current wave of low social cohesion and authoritarianism is caused by recent technological advances. Indeed, this phenomena I'm about to describe is a precursor of war, but the causal relationship is the inverse of your suspicions. And I think it can also be fixed by other recent technological advances. Here's why and how:
The Internet and social media in its current form makes it easier for social groups to get larger and more intellectually and ideologically homogenous. As these groups get larger, it becomes harder for individuals to communicate across groups or think for themselves because there are various in-group moderation mechanisms (filtering, banning, ranking, deplatforming, cancel culture, etc). Eventually, the echo chambers become large enough to fight over who gets to run a nation's government. The winner turns into a government that moderates its people (like it always did before it became the government). Multiple such governments emerge around the world. This happened in cycles in the past as well, but modern technology facilitates the process.
To prevent this, we must realize two democratic principles simultaneously: "one shall have the freedom to decide what one sees and hears" and "one shall have the freedom to express whatever they like". It wasn't possible to realize both principles simultaneously in the past without a central authority because if someone is doing something in a public space, you cannot selectively filter them out. If you cover your eyes and ears, you block out not just that person, but everyone else as well. So we came up with rules for behavior in public spaces and wrote them into law. This didn't drastically raise the probability of a democratic society turning authoritarian because there were physical limits on practical group size. It was very hard to rally a large group of intellectually homogenous people. But the Internet and social media completely broke this safeguard imposed by physics. Now, echo chambers form naturally and grow rapidly.
To fix this, we must normalize not moderating or filtering content online in any centralized manner. Instead, we build user-configurable client-side content filters and ranking algorithms so that each individual can decide what they see and post, but nobody can decide what anybody else sees or posts.
We need to replace server-side content filters and ranking algorithms with offline solutions controlled by each individual on their own device. Get rid of likes and dislikes, and get rid of server-curated feeds. Have the server send a raw RSS feed of everything posted in the past day (or whatever time window, sparsely randomly sampled if there's too much) at once, then get it ranked and filtered on the user's device based on the user's preferences and viewing history, and then fetch the actual media associated with those feed entries.
This will, somewhat counterintuitively, increase social cohesion by limiting the inter-group rift between individuals and prevent the formation of large echo chambers. People will be more likely to engage with eachother in good faith. Authoritarian patterns will be more likely to naturally dissolve.