Octopi is not the most common plural, true.
> Octopus is of greek origin, not latin.
Octopus entered English from scientific Latin. In which the Greek plural was not used. (Lots of words in English fron languages other than their language of origin and have irregular English forms from their immediate source rather than their remote origin.)
“Octopi” appears to be the earliest English plural of octopus.
> Thus, its greek plural is octopodes.
“Thus” is incorrect there, but, yes, that is its Greek plural.
> And thus, since we don't tend to use greek plurals in english
But we do. Just not, until comparatively recently and never dominantly, in the case of “octopodes”.
> the other proper plural is octopuses.
That is the most common English plural, and you don't really need a (false) historical narrative to support that it is “proper” except coming from a broken prescriptivist framework.
> Octopi is what's known as a hypercorrection
Since its the oldest attested English plural, its not a hypercorrection, just (arguably) dated. Though its probably the most common incorrect example of hypercorrection.
https://www.merriam-webster.com/words-at-play/the-many-plura...