"Why did Allah Almighty create the universe?"

He created the creation to manifest His grace, justice, power, and perfection.

Belief :
Every action of Allah Almighty is full of wisdom—whether we understand it or not. It is from His wisdom that He appointed one thing as a cause for another in this world. He made fire a cause of heat, water a cause of coolness, the eye for seeing, and the ear for hearing. If He wills, He can make fire cool, water hot, the eye hear, and the ear see.

Belief :
God is free from every flaw.

It is impossible for God to possess any imperfection or deficiency, such as lying, ignorance, forgetfulness, oppression, shamelessness, etc. All such evils are absolutely impossible for God. And whoever believes that God can lie but does not, is in fact claiming that God has a flaw but hides it. Then, it wouldn't stop at lying—this logic would apply to all evils, like oppression, theft, annihilation, reproduction, and countless other defects. Exalted is Allah far above such things.

To consider any flaw or defect as possible for God is to consider God flawed—and that, in essence, is a denial of God Himself. May Allah protect everyone from such corrupt beliefs.