Three months ago, shares of rare earths companies ripped higher after MP Materials (NYSE:MP) unveiled a game-changing deal with the U.S. Department of Defense that marks the most aggressive federal intervention in the rare earths space in decades. The DoD-backed investment package will see the Nevada-based producer build out a fully domestic magnet supply chain and lock in long-term pricing support for neodymium-praseodymium, the critical alloy used in everything from fighter jets to iPhones. MP shares doubled in a matter of days, with the…