Supposedly, the victim was not a Trump supporter but rather “his belief is that it’s necessary to break down the political bubble we all find ourselves in and to get used to interacting with people who have different perspectives. So by wearing the hat to the rally, he hoped to present an example of a non-crazy Trump supporter to the liberals there.”
“He said that he wants to see political discourse return to a less vitriolic state. To see people discussing their views without wanting to kill each other.”
See the letter explaining the situation written by a supposed “friend of the victim” here
I don’t know if this is true or if he was a closet Trump supporter not wanting to be outed to his friends so he made up an excuse. I doubt we’ll ever know.