OP doesn't realize that DAI has sailed through falls in ETH value of far more than 50% (I think the worst was over 90% in 2018)
OP, despite his obvious great intelligence, doesn't realize that another, stronger question about DAI would be the potentially-worrying linkage to USDC etc to provide stability (though critics should note that even before that stability module, PSM, was introduced it had never deviated by more than 1%, AFAIK)
Seeing that this is, despite all those errors and omissions, the top comment here, is extremely dispiriting
Dai is now backed by a lot more tokens than just Ether, and 150% is really the minimum to avoid liquidation (145% now).
https://daistats.com