- Otherwise, a simple 51% attack will do some work to destroy the reputation.
This remains to be seen. I mentioned this scenario briefly in my last post: if there's not much damage (in terms of double spends) done, then it could be possible that BTC recovers relatively fast, as did most of the altcoins which were 51% attacked until now. And if this happens, then all the effort of the state was in vain, and even such an attack would be expensive.
A big dictatorship like China or Russia could perhaps be tempted to perform this type of attack anyway because they could try to hide the attack, as they don't need to care that much about transparency. But for any government of a democratic state such an attack would be basically suicide - why should people pay with their taxes for an attack on a tool that e.g. 10% of the voters already use? This would be a major scandal. In China or Russia it could work to hide it, but there are risks that such an attack could destabilize the government if there are traitors leaking the attack. I believe even in the most aggressive and authoritarian of the big dictatorships, Russia (and much less China) they aren't that dumb to waste billions on that.
The only actual constellation I can imagine is an intelligence department of a dictatorship performing the attack, but sponsored in secret by several other countries (every government contributing with, let's say, less than $1 billion, which perhaps can be hidden). But even there, all participants would be at risk to destabilize.
Thus a FUD & Regulation attack is much more promising. But if they go too far the attack could impact in public opinion against the governments and could lead to resistance, like we've seen in the European Parliament. The more Bitcoiners we are, the less likely is such an attack. I think for a completely destructive attack of this kind thus it's already late.
We could also speculate: was Ordinals such an attack?
The idea itself is not bad for a malicious entity - create some service on top of Bitcoin that lowers the utility of the chain for most users because it clogs the blocks, but leads to profits for a sub-group like the NFT investors and can even return the cost of the attacks from "greater fools" (like those buying ORDI at $60 or more). However, due to the way such "trends" work, sustaining such an attack would be very expensive too. And we can already say that it probably failed, because Bitcoin became even more popular. The long term solution to make such a "spam attack" much more unlikely would be - second layers (sidechains, rollups and LN).