Explanation A. Trump is a moron who can't tell the difference between the words of rhetoric and the implications of rhetoric.
Explanation B. Trump isn't appealing to neo-nazis per se. He's not trying to court people who march with the NSM or the KKK, they're too small of a demographic. He's trying to court the millions of people who think slavery had redeemable elements, or that America is inherently superior to other nations, or who think that communism is more despicable than fascism, or especially those who are incensed by leftist protestors and dream of being attacked by them so they'll have an excuse to gun and/or drive them down. That's not a majority group, or even a particularly large minority, but it is a statistically significant one and a part of Trump's loyal base.
Most of those folks would give "nazis and antifa are two sides of the same extremist coin" a fair shake.
I've also mentioned this before, but apparently a lot of modern neo-nazis and associated nutjobs have taken extreme mental gymnastics to the reality of Judaism vs its appearance in fascist rhetoric. Under this amazingly transparent re-framing, there are two groups that constitute the Jews: "Hebrew" people, who are just normal folk and used as a smokescreen, and "actual Jews", who are the shadowy globalist conspirators.
This proves the long-suspected hypothesis that reframing may be used to justify literally anything, and that indeed there is no verifiable difference between truth and lies in the practice of human communication.