You may have noticed that the plural of "tooth" is "teeth," not "tooths." The plural of "foot" is "feet." The plural of "goose" is "geese." ...so why is the plural of "moose" just "moose" and not "meese"?
It's because of the timing.
English has Germanic roots. To make words plural, the medieval Germanic languages would change vowel sounds instead of adding an S. But moose live in the New World. By the time English-speaking explorers ever saw their first moose, English had grown into its own language with its own way of pluralizing words.
As with so many other things, the English-speaking explorers asked the local Native Americans what to call the animal. They said "moose." There might have been a few guys who said "mooses" early on, but it didn't catch on. By then, no one would have thought of calling them "meese."