There is some truth on both sides of the Gottlieb resignation story as it unfolded.
Gottlieb is not resigning immediately. As he old Trump in his letter, he will submit his actual resignation letter in a month or so; his plans[and principal goal] with FDA to eliminate the source of nicotine [addiction] and tobacco[cancer, etc.] from the hands of persons under the age of 18 are now in process of being carried out and completed.
Simply put, he is tired of the weekly RT commute from Connecticut to Washington, DC; he misses his wife and 3 children who have remained at home in Connecticut while he is in Washington or travelling elsewhere.