mdd,
you do not realize the unbelievable chashivus ascribed by Chabad to the statements of Arizal.
You’re not the first one who asked this strong question.
In the letter of the Rebbe that I quoted above, he writes: צריך עיון גדול
Indeed, this is a great question.
In a later letter (אגרות קודש טז שבט תשכ”ב – אגרת ח’שלב), the Rebbe points out a possible way to solve the argument: The difference between the Rambam and Ramban (that the Arizal meant) is that the Ramban studied Kabbalah during the main part of his life, because this was connected to his שרש הנשמה.
Whereas, the Rambam only studied at the end of his life, as it’s possible that it was בבחינת עיבור (neshoma stuff – I don’t understand exactly).
it is accepted by Klal Yisroel – from the Litvishe to Sefardi Mekubalim that Rambam did not learn Kabbolah
Were the Shomer Emunim and Avodas Hakodesh not great mekubalim?
Is the Migdal Oz not an accepted peirush on the Rambam?
And the Abarbanel?