Your assumption is the reason his content was removed was because of the allegations, which is potentially not true. While it's very likely the allegations are what drew attention to it, it doesn’t mean there wasn’t a bunch of stuff there already that violated policies – especially given the content he had doubled down on.

All Youtube did was cite their “Creator responsibility“ clause[1] as the reason. This could have included a myriad of violations, especially considering the type of content he was producing.

Also, if you read the allegations, he very much was in the protected status you mention. “Open secret”, lots of people covering for him, running interference, etc etc. Calling him a “D-list celeb, likely with little to no major influence” illustrates your lack of research into the issue.

[1] https://support.google.com/youtube/answer/7650329?hl=en as the reason.