Walliams writes his own books, no ghostwriter and he doesn't take well to being edited so you can trust that the bad stereotyping, racism, sexism and classism in the books are all his own work.
Baddiel also writes his own books. So does David o Doherty. Pretty much every sportsperson, chef, reality star or general celebrity has a ghost writer but the comedians are more likely to do their own work.
Some celebrities genuinely feel like they wrote their own books when essentially all they've done is told their ghostwriter they want a character based on them (little girl who loves horses, ballet, etc) and nodded along to a few of the plot ideas put to them.
The thing I haven't seen about Walliams yet is that his PR essentially acted as security on his school visits - but security for the girls at the school, not for him. Became a thing after an incident at one school during an award event. Most of the reports about him, which go back years, are from young women from his publisher's PR department and are both about what they've had to deal with from him and how he's behaved with others while they were working with him. Plenty of cases of him sending inappropriate messages to girls on social media too.
( Meanwhile I may as well say that the Scottish DT being mentioned on this thread despite afaik not being someone anyone has referred to is very lovely.and extremely gentle and respectful in person, haven't heard anyone who has worked with him have a bad word to say. Just my personal experience.)
Anyway there is a lot to come out on Walliams but a number of people have taken payments for NDAs so it will be interesting to see what actually emerges. The author Kiran Milwood Hargraves once posted a Twitter thread with all the stories she had heard (first hand) about Walliams and nothing came of it at the time. He and the Murdoch empire have been incredibly good at silencing people for a very long time. I hope this is the end of the run for him with this behaviour.