TV tropes has a trope called "Our Dwarves are all the Same".
It has a section listing many works were the nonhuman dwarves are very similar to standard nonhuman dwarves.
This trope has an alternative title "Our dwarves are different" and includes sections depicting nonstandard and even bizarre dwarves in various works of fantasy. And TV Tropes has a whole series of tropes called "Our _____ are different", about the wide variations in the depictions of fantasy creatures with the same name between different works of fantasy.
In short, there is no reason to expect that Marvel movie dwarves are identical to Marvel comic book dwarves, or that Marvel comic book dwarves are identical to dwarves in other fantasy stories.
The OP wonders why a nonhuman fantasy being called a dwarf is not short like a member of the human species called a dwarf. In English the word "dwarf" is used for both an unusually short human and a member of the nonhuman species from mythology and fantasy.
This use of the same name creates the expectation that nonhuman dwarves in mythology, fairy tales, and fantasy are short, like human dwarfs are short. And many illustrations, films and TV shows depict nonhuman dwarves as being short like human dwarfs, increasing the expectation that nonhuman dwarves are short like human dwarfs.
But has the same word been used for nonhuman dwarves and human dwarfs since the beginning of the English language?
The modern English word "dwarf" for a human of short stature has evolved over centuries from Old English.
The use of dwarf in English for a member of a nonhuman intelligent more or less mythological species is first known in 1770, and is from German.
I tried an auto translate program and "dwarf" in English translated into German as zwerg. Zwerg seems to have both English meanings, a small human and a nonhuman mythological being.
As well as I remember, most of what we know about Scandinavian mythology comes from the writings of Christian medieval Icelanders like Snorri Sturlusson.
"Dwarf" is translated into modern Icelandic as dvergur, and it is possible but not certain that both zwerg and dvergur have the same root in ancient Germanic.
Anyway, I have to wonder if the word(s) for mythological dwarves in pagan Scandinavian languages was also used for unusually short humans, or if there were two separate words.
I don't remember ever reading any mention of the height of mythological dwarves in reading about Norse mythology. I have to wonder if all Norse dwarves were shorter than humans, or if they were sometimes taller, sometimes the same size, and sometimes shorter, than humans, as is the case with some other supernatural beings.
Tolkien's dwarves were based on Norse mythology and short, about four or five feet tall I guess, but it is possible that Tolkien added the short size to his dwarves and it was not in the original mythology.
Thus we may need an expert on Norse Mythology to explain.
Here is a link to another question:
That has drawings of trolls from four different Scandinavian countries, widely varying in size, shape, personality, etc. And I suspect that if anything it oversimplifies the varieties of Scandinavian trolls in folklore.
And I suspect that Scandinavian dwarves may have had a similar variation.