Race. I think in the end (2020 presidentail election) race was most probably the keystone of "Trumpism", at least from the perspective of the voters. Trump himself joined the 2016 presidential race (race again!) most probably to promote his brand (and his ego). Although he could well be racist, too, and not just fake his racist attitude.
But even if Trump is a racist himself, that might still be too little to prove that "Trumpism" really exists. The man has (almost) no political agenda besides enriching himself. "Trumpism" is merely an empty vessel. Mainly filled with illusions.