It doesn't even take that. Sometimes it just takes one opinion literally anywhere that one tankie sees that hurts their feelings, and they brigade away. It's totally random. I've enjoyed them doing that on shitposts and memes on sub's totally unrelated to .ml madness.
It also makes me think that there's only actually like 10 or 20 tankies that each cycle through 30 accounts each, and one guy in Beijing that runs the "Propaganda: Other Platforms" desk coordinating of all. Or maybe that's just a function of their groupthink. Hard to say.