Not sure how true it is, but I read somewhere that the reason it's so good at what it does is because it's used at scale by certain large websites (youtube being specifically mentioned).
You've got cause and effect backwards there (mostly; it goes both ways).
Disclosure: FFmpeg contributor and Vimeo employee.
I don't know of any other tool that does what it does. I used it myself when handling video and needing to re-encode or fix up output captured from elsewhere. Its a swiss-army knife of video operations.