The categorical imperative is supra-personal and isn't grounded on personal views but objective realities. This, however, is merely the reasoned view that moral laws—actionable laws—that are incapable of perpetuating themselves can't, per Pure reason, exist as supreme ENDURING laws. Keyword enduring; I.E., given that appearances are all, and these lack in themselves ontological good/bad, then if there IS a supreme moral law it both A) can't be founded on those objects, and B) can't destroy itself.
The categorical imperative is worthless as a moral law in itself, as there can be no Ought from an Is; it CAN have moral legitimacy if we suppose a transcendent Being that DOES ground a morality. This is then INFERRED (and thus the Being's, God's, existence is synthesised to the categorical imperative, granting it nothing in itself (as it's solely of pure reason), yet still justifying adhesion to the law from the belief of a God), by the existence of our moral Conscience, to imply the existence of a God.
Conscience > Freedom > Morality = God > Soul. Simple as.