Unlike YouTube, which trans-coded uploads into multiple formats, static video sites simply wrapped whatever FLV you gave them. If that FLV used an obscure codec (e.g., Sorenson Spark rather than VP6), even the original file may be unplayable today without legacy tools like VLC with FFmpeg.
However, the DNA of those early static video sites remains. Every time you watch a TikTok or a Netflix special, you are using a streamlined, evolved version of the path blazed by those old SWF players. Conclusion which trans-coded uploads into multiple formats
To enable modern browsers to render and play legacy .swf (Shockwave Flash) and .flv (Flash Video) content without requiring the discontinued Adobe Flash Player plugin. Sorenson Spark rather than VP6)