Chrome extensions are ridiculously easy to trust. Chrome can't protect you from every bad update simply by showing another permission box, especially when malicious code abuses access an extension already had. Chrome already performs some of that checking and can flag installed extensions that have been removed from the Chrome Web Store. For many users, Chrome disabling the extension was probably the first indication that anything had changed. If it does turn out to be malicious, there are a few cleanup steps worth taking after removing a bad Chrome extension rather than assuming uninstalling it ends the story.