here the thing, if they were to have enough incentivised people to buy 2,000,000 asics at $4k each ($8b)
.. then there is no point doing a 51% attack if the only aim is market manipulation... they can just market manipulate without wasting money on hardware

did you know you can produce billions of market trade volume without needing billions of dollars to trade with
think about it

if you swap ETH->BTC and then sell BTC->USD and then buy USD->ETH
you can crash the bitcoin price by repeating that circle(arbitrage) many times without needing as much funds assigned to the market campaign

again please run the scenarios and realise how there are better ways to crash a market far cheaper than a 51% attack and far faster
again please run the scenarios and realise doing a 51% attacker is more costly, slower and less market affecting