Interesting data point to contrast the models predicting the opposite. I wonder how current it is as it also says Trump would have a 95% chance of winning over Bernie Sanders. Bernie Sanders dropped out 3 months ago. It would certainly buck trends for a president to not serve 2 terms. The incumbent always has a bit of advantage as they have a free platform to address the American public and usually can point to actual things they have accomplished.
Its because the model uses the winners of New Hampshire, and South Carolina additionally as a composite if the NH winner didnt get the nomination.