Eric Berger has a good summary on the narrative: https://arstechnica.com/space/2025/03/can-nasa-remain-nonpar...
The choices were whether to leave them up there longer as the next crew rotation, or let them come home and send up another crew like normal. One would save the government the cost of a new Crew Dragon launch (not insignificant - $100m-150m), and the other would save NASA's valuable astronauts from the long term health effects of a year in space (usually crews are rotated every six months for health reasons, like bone density and muscle mass problems).
NASA reported that the factor keeping them from being brought home was cost, and they didn't have the $100m for a new Dragon launch in the budget. But this was bunk. The next launch was already budgeted for, because this is on a well-planned-for rotation. It could have been because they wanted to keep the $100m, but if they falsely claimed it wasn't budgeted for, then (as Musk postulated) it's a good bet that the real reason is that this would have been a big PR win for Musk, saving America's cherished astronauts from Boeing's massive screwup, and since he had already begun bankrolling Trump's campaign, Biden did not want him to have this PR win.