Crawling AJAX data alone makes no sense because it could be just a piece of JSON and Google needs a rendered HTML page with an URL it can show in the results. I

Crawling AJAX data alone makes no sense because it could be just a piece of JSON and Google needs a rendered HTML page with an URL it can show in the results. If you have some data that are not available at a separate URL (e.g. they are loaded when user presses a button), they will not be indexed.