Re:Intel seems awfully scared of Graviton2. Why pay for this...
by GhettoComputers on Tuesday December 14, 2021 @05:35AM
(#29550223)
https://gist.github.com/tyrell/2963c6b121f79096ee0008f5a47cf... looking at this, it seems that debian added it at least 3 years ago and even in 2016 there was a binary, unless you knew about it and it sucked.
Beyond that, I can only hypothesize that Docker on non-x86_64 (or multiarch Docker, in general), was very difficult to kick-start for whatever reason. This may have been compounded by the fact that Docker wasn't as broadly adopted by hobbyists back then, so demand for ARM builds want that great.