Worth pointing out the largest nationalist party and the largest unionist party are supposed to share power equally in the sectarian state and the only change here is symbolic. The unionist parties have insisted on the First Minister-Deputy First Minister distinction for years although it has now came back to bite them.
From an outside perspective it really seems like the DUP have painted themselves into an extremely weird corner with Brexit and their new demands that looks increasingly like it was a fatal strategic move for them from a political point of view. You already have the UVF claiming to no longer respect the GFA and it's all rather unclear where they go from here.
Excellent podcast episode on the topic from a year ago before the election obviously here talking about the context leading up to all of this along with what dissident politics looks like since the end of the troubles https://podcastaddict.com/episode/120707318