Primarily his foreign policy. I think he recognized that the president has far more power internationally than intranationally and was proactive.
Even when he initiated what doesn’t look so rosy today, like the War on Drugs or floating the dollar, he was doing them reasonably, e.g. investing more in rehabilitation than criminalization and freeing the US from being perpetual creditor.
As a Republican president in an era of Democrats he was practical and not ideological, managing to get re-elected and leave a legacy beyond the scandal that ended him publically, continuing to advise and influence policy when out of office.