They usually bind to events the browser triggers before a network request is made. This lets them literally block the browser from downloading any content from

They usually bind to events the browser triggers before a network request is made. This lets them literally block the browser from downloading any content from a source that may register your IP just from the connection (pixel tracking, etc). Searching the DOM and removing elements would still require a network request to obtain the content before realizing that it's a tracked element. By blocking the request from happening, we can truly say that an Content Blocker on iOS (for instance) speeds up the browsing experience because the request isn't even initiated.