I have no idea the details about that study but if the American public is that out of touch with reality than we deserve to re-elect trump and become a failed country.
My guess though, is that they did a poll that included 1000 republicans and 100 democrats or some such thing in order to get the desired horse race results that all the news organizations want.
The real question we should all be pondering is how did we get to the point where a president who was impeached twice for credible reasons and now under multiple indictments for some of the same credible reasons is not only remotely going to be one of our party’s nominee for President but by far the most likely nominee. There is something terribly broken in our country when 40% of the population enthusiastically supports a candidate of that (lack of) character.