God sends judgment
Isa 5:25 Therefore is the anger of the LORD kindled against his people, and he hath stretched forth his hand against them, and hath smitten them: and the hills did tremble, and their carcases were torn in the midst of the streets. For all this his anger is not turned away, but his hand is stretched out still.
God's judgment; they wanted to worship false god's and to live in sin and drunkenness, so God brought wrath upon them according their covenant with Him.
Isa 5:26 And he will lift up an ensign to the nations from far, and will hiss unto them from the end of the earth: and, behold, they shall come with speed swiftly:
God also used foreign nations to come against them, as part of his discipline upon them. He will hiss unto them, he will whistle to them, to alert them. Perhaps as an owner would say to a dog; sic em!
Isa 5:27 None shall be weary nor stumble among them; none shall slumber nor sleep; neither shall the girdle of their loins be loosed, nor the latchet of their shoes be broken:
Isa 5:28 Whose arrows are sharp, and all their bows bent, their horses' hoofs shall be counted like flint, and their wheels like a whirlwind.
God was for this, so the enemy nations would come with power unhindered by Him.
Rom 13:1 Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God.
Isa 5:29 Their roaring shall be like a lion, they shall roar like young lions: yea, they shall roar, and lay hold of the prey, and shall carry it away safe, and none shall deliver it.
1 Pet 5:8 Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:
Isa 5:30 And in that day they shall roar against them like the roaring of the sea: and if one look unto the land, behold darkness and sorrow, and the light is darkened in the heavens thereof.
Jer 6:23 They shall lay hold on bow and spear; they are cruel, and have no mercy; their voice roareth like the sea; and they ride upon horses, set in array as men for war against thee, O daughter of Zion.
Why should God help a people who forsakehim?