Its the suddenness & how seemingly unprepared the club were for it which is the puzzling thing.
the only scenario I can think of that fits is as mentioned elsewhere, The Management have offered Dai something, a change of role or a new coaching structure perhaps, & he is so unhappy with it that he's walked out got in his car & gone home, or to his lawyers office!
I guess it might be reconcilable, hence the seemingly temporary nature of the announcement....