If you look at a list of the biggest winners in today's huge stock market rally, they all have the same thing in common: They were the biggest holdings of Situational Awareness, a hedge fund started by Leopold Aschenbrenner.Aschenbrenner became something of a household name in market circles by publishing a viral manifesto on AI. He was an OpenAI research and is extremely well connected in AI circles. He parlayed that into a hedge fund that had extraordinary returns, in excess of 1000% last year and 300% just over a month ago.His secret: Highly leveraged bets on AI names like chipmakers.I bet you can guess what happened next. Leverage cuts both ways and after growing his fund to $45 billion, it looks like this week was curtains. The WSJ reports that the fund sold the bulk of its stock portfolio to Ken Griffin’s investment firm Citadel in something of a fire sale. There had been rumors of pain for Leopold and margin calls but it was hard to believe given the size of his fund. It turns out that it was true and the forced selling is what cut the legs out of SanDisk shares, one of his biggest holdings, among many of the other high flyOnce the market realized what was happening, and that the weak hand had been shaken out, it caused a rush to buy the beaten up names, which were artificially turfed due to liquidation. Other big holdings and how much they rebounded today:Bloom Energy +26.5%Nebius Group +27.1%CoreWeave +21.5%Core Scientific +20.4%AMD +13.0%Another holding was SK Hynix and that will be an interesting one to watch in South Korean trade today. Not only did his overlevered bets take down US tech stocks but they also wrecked the South Korean market, leaving a trail of margin-called traders.CNBC repots that his fund grew as large as $45 billion at the start of July before one of the greatest downfalls of all time. To put that into perspective, Citadel itself only manages $71 billion, Bridgewater manages $78 billion and Elliott manages $76 billion. Archegos was $20 billion plus around $10 billion in bank losses. LTCM was only $4.8 billion but ther weas $125 billion on its balance sheet.Now it doesn't look like he was zeroed out. The reporting says he sold the bulk (or nearly all in other reports) to Citadel so it will depend what price they paid. They would have likely got a haircut at yesterday's close, and are already siting on a sensational gain. It was supposedly at $16 public portfolio that they would have had no way of selling in the public market without crushing prices even more.So, in a way, Citadel pulled a J.P. Morgan here and saved the market.Situational Awareness also holds a reported $5 billion private stake in Anthropic among other investments. So this almost surely wasn't a total collapse but even halving the fund would rank it at the very top of hedge fund losses alongside Archegos. This article was written by Adam Button at investinglive.com.