While it's true that he resigned, it's also misleading to say so without context. As the letter says, Netanyahu is going to immediately re-appoint him Finance Minister. Now, because of the Norwegian Law, Smotrich will be a Knesset member and Finance Minister at the same time. He's doing this so that his party has more seats than Ben-Gvir's party Otzma Yehudit - they ran on one list and then separated and in the shuffle of ministers with Ben-Gvir's resignation and return, the list ended up being different than what they had agreed on. This is not without risk. Smotrich's re-appointment requires a majority vote, and Otzma could vote against upholding the agreement or the Haredim could flex muscles bc of IDF enlistment.
See Tweet