Luna didn't go to zero because the whole crypto market woke up and realized that was no intrinsic value to it. If it did, it never would've got as big or lasted as long as it did.
There was an explicit attack that crippled the peg to the point that their algorithmic stability mechanic couldn't self heal. Which led the Luna project to attempt to assist the peg by deploying their own reserves, which unfortuently didn't work.
There didn't have to be an attack for this to happen
It may have been, but it equally could have been mass de-risking due to market conditions causing lots of UST withdrawals. Once the peg goes for a minute, confidence soon follows and the whole house of cards unwinds
LFG had $1.5B of reserves to plug a hole in a $18B leak. It never had a realistic chance of working (unless it was fast enough to stop the initial depeg, in which case it could have delayed the inevitable)
There was an explicit attack that crippled the peg to the point that their algorithmic stability mechanic couldn't self heal. Which led the Luna project to attempt to assist the peg by deploying their own reserves, which unfortuently didn't work.