Astroturfing on the fediverse will probably take a different form for the time being: Since people here are above-average politically minded, with a robust tendency to the left, the attempts will probably be aimed mostly at distracting, derailing, and sowing discord and doubt. Stifling any nascent initiative, rather than garnering sympathies for anything in particular. Much like described in this post from yesterday.
How to guard against this... It feels to me like it will help vastly if as many of us as possible are also engaged in Matrix/Element channels, i.e. either channels specific to instances, or channels specific to topics (computing, politics, ecology...). Especially those who run popular communities. This would strengthen an implicit "web of trust", in that people will over time build a better impression of whom they're dealing with (after all, it's one thing to publish astroturfing posts, but a different thing to simultaneously entertain semi-personal relationships in a chatroom while never raising doubts about your earnesty). Also, whenever some of us erroneously start to mistrust each other for whatever reason, being in touch over a second channel will give us a better chance at sorting things out before a lasting rift occurs.