It prevents censorship network wide, which means you can publish no matter what and people can see it. So it prevents echo chambers by making sure nobody controls the narrative on the network.

Another way it does this is that there's no financial incentive to share "engaging" content and there's no algorithm to rank content. So it is not conducive to the viral spread of inflammatory content.

Keep in mind, most things we call "networks" are just single web sites. Most of the problem I believe stems from this confusion. AP is an actual network. It is what we have wanted to have on the internet for a very long time.