I recall that when James Corden first became popular in the United States — I believe he was in a play in New York City that immediately caught people’s attention — there was a lot of chatter among the British population. I’ve never really understood it, but maybe if he had a negative reputation among fans because of his treatment of them, this could have played a role in his poor public image in the United Kingdom.
I have to give him credit for having some really hilarious bits on his talk show. The crosswalk musicals, Carpool Karaoke, and the amusing little mini-musicals he performs with his guests are all fantastic. However, he may be unable to take responsibility for all of it because he has a staff of writers and producers working for him.