Earlier quoted context omitted.
Much larger. Static HTML AJAX WebSocket, for example weren't it decades in between?
Once Javascript became available there were plenty of techniques. e.g. refreshing borderless iFrames to load new HTML and using hidden iFrames to load new state. AJAX made it much easier but it didn't offer anything that hadn't been done before.
https://news.ycombinator.com/item?id=42850693
I did this as the front-end engineer of a high-profile site that went live well before XMLHTTPRequest.