Every word we speak and every deed we perform has behind it, a thought.
The thought which prompts the speech or the action, at its origin, is a thought about Allah.
Whether this thought about Allah is right or false ultimately determines all that develops from it. Thinking correctly or thinking wrongly about Allah is behind everything we do.
Allah refers to this in Surat-al-‘Imran as “thinking of Allah other than the truth”.
And if you think of Allah other than the truth, your deeds and speech will ultimately fail you. You will be acting, to one extent or another in a state of delusion. You will form a view of reality, make decisions, have opinions, all proceeding from error and falsehood; and of course, this can only result in failure.
As Allah says in Surat-al-Fath:
“you assumed an assumption of evil, and became a people ruined”
In both instances here, the false thought referred to the thinking of the munafiqeen that Allah would not help His Messenger and the Believers.
This is a terribly wrong thought to hold about Allah, and all the words and actions that proceeded from that thought, indeed, brought those people to humiliation and self destruction in this life and to the punishment of Hell in the next.
They made the wrong choices for their lives because they thought of Allah other than the truth.