Benzinga and Yahoo Finance LLC may earn commission or revenue on some items through the links below. Editor's Note: This article has been updated for accuracy and clarity. Magnetar Financial—once famous for shorting subprime debt—has quietly morphed into one of the biggest beneficiaries of the AI gold rush. The billionaire hedge fund manager's bet on CoreWeave Inc. (NASDAQ:CRWV) has ballooned from a modest $50 million in convertible notes into a$12.5 billion stake, representing nearly 72% of Magnetar's $2 ...