Although Sanders officially held the role of press secretary for roughly two years, one could argue that by the end of her tenure, she wasn’t exactly acting the part, at least as far as press briefings were concerned. By the end of her press secretary career, the White House had simply stopped holding regular formal press briefings. In fact, after a briefing Sanders held in March of 2019, there were zero briefings until Kayleigh McEnany finally held one in May 2020, breaking the streak.
Since Sanders herself didn’t announce her resignation, and since there were no briefings on the topic, the reasons for Sanders stepping down from her position were never really laid out for the American public. Trump simply announced in a tweet on June 13, 2019 that the “wonderful Sarah Huckabee Sanders” would be leaving her position at the end of the month and returning to her home state of Arkansas.
Given that she wasn’t fired or given one of Trump’s infamous Twitter nicknames, it’s probably pretty safe to assume that there was no bad blood between Sanders and Trump. One can also assume that her resignation is a topic that Sanders delves into in her upcoming memoir, entitled Speaking for Myself: Faith, Freedom, and the Fight of Our Lives Inside the Trump White House (slated to come out Sept. 8, 2020).
Source : https://www.distractify.com/p/why-did-sarah-huckabee-sanders-resign