It's not really a surprise that if you manually code something (with someone who knows what they are doing) that its better than a framework. Frameworks are there to help eliminate duplication (DRY), and to help people who are new to coding advance quicker than if they learned on their own, it also helps to add consistency to results. I'd always say doing something without a framework well would almost always be faster than the latter, its just hard to find good coders.
As others have said, this is a unique situation for the text editor component.
In a lot of more conventional situations, it's very likely that React's diffing code is highly tuned for performance over years and will do as good a job as you manually writing the JS, while saving you a ton of time in having to worry constantly about the DOM.
