In the Srimad Bhagavatam, Brahma speaks to Narada Muni about the source of his powers. Not only Lord Brahma but all demigods and other controllers of the universe are awarded their positions because of their devotion to the Lord. Demigods are all great devotees of the Lord who at the same time have strong material desires. The Lord thus puts them in positions where they can serve Him but at the same time live in positions of power and influence. During their long lives, the demigods can gradually satisfy their material desires and eventually go back home, back to Godhead.
Lord Brahma is thus not a separate controller. He is empowered by the Lord to perform his functions, and the reason he is empowered is that he is a great devotee.
“O Nārada, because I have caught hold of the lotus feet of the Supreme Personality of Godhead, Hari, with great zeal, whatever I say has never proved to have been false. Nor is the progress of my mind ever deterred. Nor are my senses ever degraded by temporary attachment to matter.
Although I am known as the great Brahmā, perfect in the disciplic succession of Vedic wisdom, and although I have undergone all austerities and am an expert in mystic powers and self-realization, and although I am recognized as such by the great forefathers of the living entities, who offer me respectful obeisances, still I cannot understand Him, the Lord, the very source of my birth.” (SB 2.6.34-35)
Although Brahma is so powerful, he is unable to fully comprehend the glories of the Lord. Because of his devotion, Brahma can understand to a certain extent, but it’s not possible for anyone to fully understand the opulence of the Lord, since He is simply unlimited. Just like one can’t estimate an unlimited number, one can’t understand the unlimited opulences of the Lord.
The same applies to us. To the extent of our devotion, we may be able to understand the Lord up to a certain extent, and from there we may gradually understand more, but it is not possible for anyone to fully understand Him. Even the Lord’s personal associates who live with Him in the spiritual are constantly amazed by learning new details about the Lord’s qualities and activities.
Can Krsna estimate the extensions of His opulence? As Prabhupada mentions in his purport to 2.3.26, surely He can, but because his potencies are always expanding, immediately there is something new that was not included in His estimation. If Krsna tries to estimate a second time, including the new expansions, immediately something new appears, and so on. Therefore, even Krsna Himself becomes surprised.
In this way, it’s not possible to understand Krsna by experimentation or speculation. What to say about some imperfect scientist or scholar, even a pure devotee is not capable of fully understanding Krsna. The process is thus to abandon the attitude of imagining Krsna as an object we can study and simply surrender to Him. As Lord Brahma concludes, this surrender is all auspicious and allows us to attain unlimited spiritual happiness.
“Therefore it is best for me to surrender unto His feet, which alone can deliver one from the miseries of repeated birth and death. Such surrender is all-auspicious and allows one to perceive all happiness. Even the sky cannot estimate the limits of its own expansion. So what can others do when the Lord Himself is unable to estimate His own limits?” (SB 2.36.36)