A former chief sanitary inspector of Russia, Mr. Onishchenko, recently said the following about the chief infection control doctor of the Stavropol region, Ms. Sannikova:
Она долго работает инфекционистом — вот и притупилась бдительность. Не врачам этого не понять. (Source)
I got very much confused by the construction не врачам этого не понять. It is the first time I see a grammatical construction like this. I am confused as to whether the construction is grammatically and stylistically correct and what is its meaning.
The context is that Ms. Sannikova visited Spain, got infected there with the novel coronavirus, returned to Russia, and resumed her work as usual, engaging in close contacts with a dozen of Russian lecturers and a dozen of students and failing to test herself and observe basic self-quarantine measures.
My question: Is the expression не врачам этого не понять grammatically and stylistically okay? If so, what is its meaning?