Simplicity, in Solomonoff's theory of inductive inference, is based on minimum description length, i.e. the length in bits of the computer program that can produce the specified output. How long would be the computer program that could simulate God and everything God does? I don't think it would be very short. Certainly it's not "perfectly" short, because we can enumerate all the 0-byte or 1-byte computer programs in any particular language, and none of them simulate God.
Intelligence might not actually be that complex. AIXI is a relatively short computer program that also would be a full general intelligence if it only had enough computing power (which it will never get, as it takes exponential time). But the concept of God includes more than just intelligence, it also includes certain behaviors such as love, which don't seem amenable to a simple encoding as a computer program.
But perhaps some abstract version of love could be somewhat simple. Maybe a concept like, "favoring outcomes containing intelligent agents achieving their goals," could be written into the reward function of an AIXI-like computer program.
However, the probability of the God hypothesis H, given all our observations O, is written like P(H|O) = P(O|H) P(H)/P(O). The simplicity of God - the shortness of the shortest computer program simulating a being with the properties of God - affects only the P(H) term. The P(O|H) term is "how likely that we would see the exact set of observations we do see, given that the universe was created by this exact computer program." And because we have no idea what specifically such a computer program would do, because it would act as an inhuman superintelligence, P(O|H) would be very low. And that means P(H|O) wouldn't be very high either.
You need to compare it to a physics-based explanation, which would also be a fairly short program encoding simple laws of physics. But it would match only the exact physical laws we do see around us, which would give it a huge advantage in the P(O|H) term compared to God.