I think its important to specify here that “poor hygiene” includes putting soap and other stuff on or in the vagina - stuff that for many other body parts would be good hygiene.

Proper hygiene consists of clean underwear every day, mild unscented soap on mons pubis and outside the vulva (thighs, ass), and only water on the outer parts of the vulva (labia, clitoris etc), and absolutely nothing inside the vaginal canal. The vagina is constantly flushing itself out, and trying to clean it’s inside is only ruining it’s process of self-cleaning.

Infections are most common when unsuitable stuff is introduced to the sensitive environment: perfume, soap, poorly washed sex toys or body parts introducing bacteria; or choosing wrong material for condoms, sex toys or underwear. Not washing or changing underwear can also lead to strong smells, but is by far not the most common one reason for infections.