I don't understand what the big deal is. I heard he "resigned" and thought oh okay, that was quick...moving right along as planned. And yes, that's what I figure. It's just more nonsense to drive up ratings and views.
Yawn.
Welp, I found a decent article that brings up what I heard before. There was talk of Sessions leaving (by hook or by crook) after the midterms, and it also coincides nicely with Mueller's report that, shockingly, Rosenstein actually wants to be wrapped up, too. Article posted 17 Oct 2018.
Just...
full article: https://www.washingtonexaminer.com/jeff-sessions-sent-trump-a-resignation-letter-in-may-after-humiliating-oval-office-meeting-report
Edit: Not just months...over a year ago-Sept 2017.