Yep, dormant bots waiting to be activated had been brought up before, but nicely fleshed out theory 👀
It could be any malicious actor, political or just an apolitical troll, prankster etc. Probably no way of tracing their origin or even knowing if/when they do get activated, in this scenario.
I suppose not making in nostr is incredibly low cost/effort, so it could be someone with grander perhaps political motivations, thinking about a 'just in case nostr gets big in the future' presence established here. Perhaps happening in all the other twitter alts too ¯\_(ツ)_/¯