I think that the Luna treasury alone is not able to make the entire cryptocurrency market drop so drastically.
Imagine you are shorting 50k bitcoin to the market. that's enough to create very big pressure to the market like this time. Terra luna keeps selling their bitcoin for UST but again market will decide whether they will trust UST again or not.
A wallet with 10 millions UST already lost a lot for did nothing. this is a big shame for this foundation.
However, the financial security of Luna that you write about seems to me very unstable and in my opinion this may be one of the reasons why this project may be in danger of collapse.
Only stupid developers will introduce stable token in valued pegged with fiat money but it's not using fiat money as a way to make it stable or backed it. How dumb these developers are. If bitcoin will be dropping so hard and that will be the end for the foundation