Crypto researcher Small Cap Scientist suggested on June 9 that the sell-offs may have been triggered by a "canary in the coal mine": a 50,000 stETH (nominally worth $45.8 million) sell-off by Alameda Research, a trading firm founded by Sam Bankman-Fried. SCS also reported that Celsius Network was "quickly running out of liquid funds to pay back their investors", and "they are taking massive loans" against "billions in illiquid positions" to pay back customers.
Lido-staked ETH, a project that offers to allow users to stake ETH for the purposes of securing it after the Ethereum "merge" — that is, the ever-delayed move to proof-of-stake. Although stETH is backed 1:1 with ETH, it's not very liquid aside from the primary liquidity on Curve. Huge sell-offs of stETH for ETH have been causing slippage in the Curve pool, which was off peg by around 5% and heavily imbalanced on June 12.