Isaacman, who flew on two private SpaceX missions and funded the first-ever private spacewalk, was expected to bring leadership stability to NASA, which has been under temporary management since January. His nomination had already passed a key Senate committee.

Sources told the New York Times that Trump was upset to discover Isaacman donated to Democratic Senators Bob Casey and Mark Kelly—himself a former astronaut—as well as the Democratic Party in California. Isaacman had also contributed two million dollars to Trump’s own campaign.

Some see the move as part of a growing rift between Trump and Elon Musk, whose company SpaceX dominates the U.S. space industry with major NASA contracts. Meanwhile, NASA faces a budget cut of about twenty-six percent next year—mostly affecting research—while one billion dollars is being added to push a crewed Mars mission, a project currently led only by Musk’s company.

With Isaacman’s withdrawal, NASA is left in limbo once again, as critical programs and jobs hang in uncertainty.