There can be an explanation for usage (the tallest building in the world). Usage is not an explanation in itself!
The Chrysler building was the tallest building (of all the buildings that existed) in the world. Today, it is the seventh tallest building (of all the buildings that exist) in the USA.
He was the most valuable player (of all the players who were) on the team.
Superlatives are made with 'of', definitely, but the part that contains this preposition is understood in the sentences above! That is why one might be under the mistaken impression that superlatives can sometimes be made with 'in' or 'on' instead of 'of'.
I say... whenever you want an explanation other than 'that's usage', ask... a non-native speaker of English!
We, learners of English, have trouble with what you, dudes and gals, say... because of what you do not say!