Trying to think of an issue that was 1) really important to Republican voters, 2) a Republican president made huge progress on it, and 3) those voters had no idea anything had happened. Can't come up with anything.
Similarly, most GOP voters today have no idea what Trump did with a few early EOs to hamstring a lot of federal agency rulemaking, or the chaos he caused by maxing out the use of "acting directors" across the federal govt.