Extreme statistical outliers dominated swing state voting patterns, across all swing states.
Trump got far more "extra votes" than Harris in swing states, both when comparing to downticket races within the same state and when comparing to mom swing states.
Republicans had a known substantial contingent of "Never Trumpers" who vote Republican but not Trump, but Democrats who vote Democrat also supported Harris. ("Moderates" who claim to be tired of "progressives" vote Republican, not Democrat-but-not-Harris)
Where did these tightly correlated extra votes come from?
Data and analysis at The Numbers are Wrong:
https://www.thenumbersarewrong2024.com/across-the-us/swing-states