I'm wondering which historians you are talking about. Many historians called Reagan out at the time and have written very critically about his time in office. One of the most significant trend in the academy over the past sixty years has been the many steps towards the inclusion of all voices in the researching and writing of history.

Some people even believe there is now a refrain that says no white men need apply. Granted there is a popular history that is very different. Historians will fight over Trump's legacy for a long time. My bet is that twenty to thirty years from now Trump's historical reputation will be much worse than it is today.