I think the list of good things that Trump did was rather short, but the biggest two were unintentional.

1) He totally upset the "natural order" of Washington politics, and we got to see a lot more of how people really think in the last 4 years as in the last 40; and

2) He ripped the mask off of US policy, most particularly foreign policy. All the same horrible policies, but discussed openly (e.g. "we should take the oil.")