An answer to those questions would be better served with additional context. Who were those people voting for before Obama? Is Obama the outlier for them or Trump?Why are there so many Trump/Obama voters? Or instance, a bunch of voters as who swung from Obama to Trump. Same with counties, states, etc.
Are you suggesting that voters who swung from Obama to Trump got more racist in between those election?
Also, what would be the explanation for voters who swung from Biden to Trump?
Regardless the amount of people flipping back and forth is not the majority.