Going from what currently seems to be popular: huge botnets that carefully try to curate "real" users from random accounts. Rolling your own (Network that is, like FB or TikTok) seems pretty unlikely regarding initial investments, user base etc.
It seems more sustainable and much easier to work with if you have your own network, and you don't rely on US-services looking away / Twitter tolerating your stuff.
For a bad actor, the cost-reward looks pretty low (if we assume a high initial investment like a couple hundred million dollars to approach our goal of data collection in a shorter timeframe), but for a government that is probably totally doable.