It seems worth noting, to add a little context, that Sunstein ran the White House's Office of Information and Regulatory Affairs for the first few years of the Obama-era, and at least per a Harvard press release in 2018 is by far the most-cited legal scholar in the US.
He's probably best known for "nudging", but some of his other research interests I think are at least as interesting and which may explain some of the blowback he's gotten. I'm thinking here of things like availability cascades and preference falsification (though the latter is better associated with former coauthor of his, Timur Kuran). If you're interested in trying to get an overview of his thought, he was recently a guest on the 80000 hours podcast discussing How Change Happens. He's also almost certainly the highest profile academic to have written for Quillette, where he published Conformity and the Dangers of Group Polarization, an excerpt from a recent book of his.