Glorious promises in the beginning of Isaiah 9. And then, from 9:8 through 10:4, the great and coming demise of the northern kingdom, of which the birth of the child Maher-Shalal-Hash-Baz was a declaration, is elaborated.
That demise of the northern kingdom (Samaria) takes place almost 140 years before that of the south, but Isaiah knows and has been warning that Judah is headed down the same road, infected with the same rebellious heart. The fulfillment of this chastisement upon Samaria is to be timely warning to Jerusalem.
She would not listen.