Hmm. The trick with Giphy is to use their "Copy Link" feature to get a link directly to the GIF itself. If you link to Giphy's landing page for a GIF, then it'll be treated as a web page link rather than an image link (I think maybe that's what happened there?).
Btw, the editor really is WYSIWYG, so no need to publish to see what the embed will look like. 🙂