Was it loading any Flash or it was a Flash app provided by the website that you could upload your content to?
I know of a certain adult website which hosts "webteases", which are basically interactive/choose your own adventure slideshows. The content was originally provided with Flash, but now they reworked it to use HTML5 and most of the content seems to work because it was using the website provided framework for the content.
IIRC, you would upload wav or mp3 to YTMND, and then it would play back in Flash. I think it worked like this for one or both of these reasons:
1. Syncing the audio and video. It is difficult to sync a gif with audio. They have to be started at the exact same time, be the exact same length, and never get out of sync due to lag/stutter. This wasn't important for early YTMNDs, but mattered later when people created what were disparagingly referred to as "___ short films".
2. Bandwidth. I think Max had said the Flash solution was more efficient than serving the raw audio and gif. Think of it as an early version of WebM.
I think the use of Flash could be controlled on a per-YTMND basis - the creator could disable the use of Flash. And/or maybe it was that Flash was only used for animated gifs?
I know of a certain adult website which hosts "webteases", which are basically interactive/choose your own adventure slideshows. The content was originally provided with Flash, but now they reworked it to use HTML5 and most of the content seems to work because it was using the website provided framework for the content.