Chulin 7b, memra of rabi chanina – ain Odom nokef etzbao ele im kein machrizin etc…
The rambam in yad, hilchos taanis 1,3 אבל אם לא יזעקו ולא יריעו אלא יאמרו דבר זה ממנהג העולם אירע לנו וצרה זו נקרה נקרית. הרי זו דרך אכזריות וגורמת להם להדבק במעשיהם הרעים. ותוסיף הצרה צרות אחרות. הוא שכתוב בתורה והלכתם עמי בקרי והלכתי גם אני עמכם בחמת קרי
Moreh nevuchim is anything but “clear”. Rav chaim brisker told the brisker rov not to learn it when he was young, even though he himself did. He also told his son to think of ain ohd milvado when jn trouble, that there is no power or cause besides Him. It’s also translated from Arabic. My thoughts are that the rambam is referring to all of klal yisroel when he says chasidav, l’afukei goyim. Other achronim make this point without referencing the rambam, that hashgocha protis in its full extent is for klal yisroel and not goyim. We find elsewhere that klal yisroel are called Hashem’s chasidim and “yireim”, if they’re keeping the mitzvos.
The rambam in yad is much clearer. There are tons of pesukim that eschew Mikrah(happenstance) and tell us to ascribe everything to Hashem. The chovos halevavos is also very clear about this in shaar bitachon, as is the sefer hachinuch on jealousy and revenge. He happens to hold that animals and plants are hashgocha klalis, like the rambam you quoted, but the achronim don’t go with it, especially in light of the zohar which has many statements to this effect.
Hashgocha protis in the way the yiddishe mames taught us is the mesorah for klal yisroel, especially after hisgalus hakabalah; it’s not a coincidence that seforim such as the nefesh hachaim, which were based on an understanding of chazal in light of kabalah, stress these issues very much. For us to accept the views of rishonim would be – itself – denying hashgocha in Hashem’s guidance of the flow of the development of hashkofa/mesorah throughout the generations. It’s for the same reason that rav elyashiv banned slifkins books, even though he may have had rishonim supporting some of his views. We don’t have authority to revert back to the rishonim if Hashem has guided the way He wants us to serve Him through the mesorah of the achronim that’s the point the chazon ish in iggros makes about finding kisvei yad and using them to overturn rulings of schronim.