In that case they were the custodian for hedge funds assets. Lehman held those assets, in some cases because the British government force them to.
This really caused 2008 to spiral as now hedge funds that were perfectly fine got locked up and had to pull assets from the market due to Lehman holding their assets which caused even more selling and the feed back loop continued as funds sold their best assets first(think the Microsofts of stock world).
A coin bankruptcy would be the same thing, retail probably doesn't matter too much but if COIN held institutional funds, those guys do need to have liquidity for redemptions. This would mean alto of sell pressure on other exchanges and would lead to the best and highest quality crypto assets getting hammered down as funds fled to cash/stable coins.
Solana would probably crash and then shut down the network, even though they still try to claim they are a decentralized network:)
ETH and BTC would see very sharp drops in the first few days and then bounce back as people need to put money somewhere.
DEFI would feel this sell pressure and have alot of failings due to liquidity pools bein drained in this rush to quality. At best they'd get shutdown, at worst they'd just fail and go away.
You'd also expect the algo based stable coins to break the peg, even the well collateralized DAI would probably break.
Tether would probably continue on just fine as that's probably what most institutional funds would go to and I've given up on trying to predict its demise,