"He ran the fastest." 'the fastest' is an adverb here, not a noun, so why does it use the definite article 'the'?
We could say "He ran fastest", and that works fine too.
If we say "He is the fastest runner", 'the' relates to the noun 'runner', so there is no problem--so the fact that superlative adjectives also have 'the' in front is not an issue…
But if we say "He is the fastest", is 'fastest': 1. a noun? 2. a predicate adjective, in which case why does it take 'the'? 3. an adverb--which is odd, because it would translate like 'He exists the fastest'? But then, you can also say "He is fastest".
There would seem to be some serious blurring and confusion here between 'the fastest' as a noun, an adjective and an adverb. "He is the fastest runner", "He is the fastest", "He ran the fastest", "He ran fastest", "He is fastest".