In the EU the platform becomes responsible for posted content, the moment someone notifies them that they are hosting something illegal. They have plausible deniability until notified, after which they have a certain time to act, and if they don't they are criminally liable. The user posting the content is also liable, from the moment they made the post.

Are lewd drawings illegal? To my knowledge unless they are real photographs then it is legally fine, if disgusting.