1- Allah’s powers are infinite. If he wants something instantaneously, He just commands it to happen and it happens. He doesn’t need to seek any steps to achieve it.
2- However, Allah is wise and Has a system. He created the universe in 6 stages. One reason is to teach us to be organized and do things step by step—not to rush into things without a proper plan. Also, He created the universe in stages so we can see how those stages formed and we can better appreciate his knowledge and power. If something is created instantly, you don’t know how it was made.