Muhammad - 47:11
Because Allah is the protector of the believers. The disbelievers have no protector.
The gods of the destroyed tribes could not help them:
The Sandhills/46:27
And how many cities around you We destroyed, and We explained to them the Verses that they might return.
The Sandhills/46:28
Should not the gods they had taken besides Allah to draw near to Him have helped them? Rather, they abandoned them. Such are their lies and fabrications.
The Forgiver/40:21
Do they not travel in the earth to see what was the outcome of those before them? They had more power than them and were more productive in the earth. But Allah seized them with their sins. There is no one who can protect them against Allah.
The Thunder/13:11
(For each of them) there are those who watch him from in front of him and from behind him. They guard him by Allah´s command. Unless a community changes itself, Allah does not change their condition. And when Allah wills evil for a people, no power can stop it, nor do they have any protector except Him.
Prophet Hud/11:100
What We have related to you is the news of those cities. Some of them are still standing and some of them have been slaughtered.
Prophet Hud/11:101
We did not wrong them, they wronged themselves. When the command of their Lord came, the gods they invoked besides Allah could not save them from anything. In fact, it only increased their loss.
The Stories/28:81
We drove him down into the earth with his house, and he had no company to help him except Allah, and he was not of the victorious.
The Cave/18:37
"His friend who spoke to him said to him: "Do you deny your Lord, Who created you from dust, a tiny drop, and formed you into a man?"
The Cave/18:38
"As for me. Allah is my Lord, and I do not associate anything with my Lord."
The Cave/18:39
"Should you not have said as you entered your vineyard, ´This is a gift from Allah, and strength is only with Allah´? You may see that I have less money and children than you, but"
The Cave/18:42
"Then its produce was destroyed. And he began to mourn for the labor he had put into his vineyard, whose arbors were piled upon it, and he said, "I wish I had not associated partners with my Lord."
The Cave/18:43
He could not find any support to help him except Allah. Nor could he save himself.