It's the combination of catalyst accounts and the army of signal boosters that allows the disinformation to spread quickly and reach the mainstream.

There are multiple, powerful forces waging a psychological information war against the American people. The Trump campaign (and administration) has made use of it and contributed to it, but they don't control it, and possibly don't fully understand it.

The most polarizing claims are the most repeated by these bots, and as readers see them in aggregate over time, they become more plausible in our unconscious mind.