yeah, i might be misremembering but i'm pretty sure that signature malleability was the big problem for lightning because the state is only settled at the end of the life of a channel
segwit was the solution for this that stayed with the ECDSA signatures, by augmenting them with some extra jazz that does things that stop you from being able to jiggle the bits to have a good signature refer to a bad data
what malleability means is where you "mine" on the signature data to have it generate the same hash as the one the signature applies to, with ECDSA, this is a larger number of possible values, but with schnorr it is only one, and thus it can't be "malleated"
it's actually the big flaw in ECDSA that is the biggest shitty factor in the timeline path of bitcoin because if bitcoin had been released a year or two later it could have been using schnorr signatures from genesis, and there never would have been this vulnerability in the first place, and lightning would not have benefited from it
and i should also point out that taproot is retarded, i don't even understand why they didn't separate the "tapscript" shit from the implementation of schnorr signatures
if you go read up on the history of the blocksize wars and the segwit bullshit you will learn about how there was a lot of chatter about adopting schnorr signatures instead
twice now, this has been fucked up, it's disappointing