His die hard fans.....are republican primary voters. These guys get off on the childishness. They love it. Its *why* they love Trump.
You may have a point about the majority of Republicans (I don't think you do, but for the sake of argument, lets go with it).....but these aren't the primary voters. You get the most die hard republicans, the most motivated, the most aggrieved.
And its going to be the hapless souls that have swallowed the conspiracy laden koolaid that Trump has been shilling. Those that thought the election was stolen, or the FBI planted evidence in Maralago, that the democrats are 'evil', or that are lifting one finger in a WWG1WGA salute.
You have sorely underestimated the sheer petulance and pettiness of the republican primary voter. If Trump goes for it, he'll easily win the primary. Because republican primary voters LOVE him for all the reasons he turns everyone else off.