Tangent topic, but how does an anarchist system prevent popular leaders from gaining authority? Also, how does it defend against an aggressive authoritarian neighbour that wants to annex territory?

I like the idea of anarchism in theory, but I just don't see how it could be possible to get there from here where every existing power would see it as an ideological threat to their own power (similar to how capitalist powers reacted to communism), or how it would maintain stability if it was realized.

And as much as I don't like the monopoly on violence system because it seems to encourage corruption on the side with more access to violence, I can't help but think it would eventually devolve into a lot of in-fighting.

Like power constantly rises from nothing more than physical strength, charisma, or good strategic thinking in groups of humans. Some primates other than humans go to war with their neighbouring groups. Egypt became a kingdom when one tribe conquered the rest, and that one wasn't the first to try. Countless empires have risen and fallen, most of the time despite violent resistance of those who would rather be neighbours than subjects. The Vikings sailed around raiding for their own benefit and then later conquered regions like in France, Britain, Sicily, and Kiev. The Mongols did the same except using horses instead of boats. Then European powers did it. Then America started pretty much puppeting anyone who went against corporate interests while a cultural movement in Russia and China started out trying to move power out of the hands of their ruling class only to see even more authoritarian powers take over.

History is full of cases of "I don't care what you want, this is what I want and I'll just kill you if you don't go along with it." How could that change?