This topic was recently discussed in the Bitcoin section. I see a minimal danger for such a "conspiracy" to work if Bitcoin is really losing the "idealistic" part of the user base completely, but I don't think this will happen, at least not soon. But as long as we have vocal voices upholding the cypherpunk ethos, the markets will follow the "honest" chain/protocol, because this particular ethos is too much associated with Bitcoin's main characteristics (censorship resistance etc.) which can be described, from a business perspective, as USPs (unique selling propositions).

Hypothetical case: if <some business> tries to convince miners that Bitcoin should change to PoS and create a way to block funds (just like ERC-20 tokens), would the miners agree? I think not, because all such a change would do is to convert Bitcoin in a poor man's Ethereum which can be censored at any time. Why should this coin then have any value? Miners will understand this case.

I however agree that we should aim for a healthy ecosystem of several decentralized, non-premined, uncensorable chains in the case anything goes wrong with BTC. And Litecoin is probably one of those chains all those interested in censorship resistance and similar stuff should also be interested to protect, even if its origins were a little bit shady (instamine allegations due to Charlie Lee's early GPU mining). XMR, Doge, maybe also Dash, RVN or Flux, and perhaps also some much weaker non-premined chains but with unique characteristics like NMC and Signum are other chains I would mention here.

No, here I completely disagree, that won't happen. This would drive the BTC price into insane regions, so they would stop accumulating eventually, and additionally this would incentive old whales to sell, leading to other coins being distributed. Also there could be compliance problems, BlackRock et al. are heavily regulated.

I also disagree that LTC should remain "unknown". The more well-known a chain is, the more secure it is (censorship resistance, ecosystem ...).