Krugman has this to say about it:
For those not familiar with how financial markets work, US Treasuries are the ultimate safe asset, used as collateral for everything. Even a hint that some Treasuries might not be honored could bring everything to a screeching halt
Musk and Trump are both in the habit of stiffing people they owe money. If markets even suspect that this habit will extend to Treasuries, God help us
It’s really difficult to tell to what level and for what end they’re trying to collapse the country. Is the goal just a grift? Is it to secure permanent corporate governance? Is it to collapse the US for techno feudalism? Is it to utterly annihilate the US on behalf of a foreign nation? All of the above by different individuals?