Why do you not believe in God?

[Mystic]

I think we can all agree that the argument is sound, but then drawing the conclusion that the God of Christianity exists because the universe had a cause is illogical, unless someone has already proved that God can create universes. Time to move on?

It seems most people are asserting not only that it's not sound, that's not valid, and not only that it's not valid, it's circular reasoning.

I don't think the God of Christianity can be proven, but I think the following you can assume of the cause:

The cause doesn't have a beginning.
Infinite time for the an assumed material cause, would not allow it to change and be the cause, therefore it's better to assume it's timeless, although can have relationship to time once time is created.
A material non-magical entity, cannot make time to begin and cause all the laws with time to begin.
Therefore a magic super being had to make time and the laws with time to begin.

Now if we go by reality is simple/indivisible, we can say it has to be intelligent and powerful, but these only can be simple and not divisible when they are ultimate.

Goodness is form of will power, and Ultimate Power would contain it. It's part of "high intelligence" and therefore ultimate intelligence would contain it.

That, and signs of creation show moral goodness. (like family, love, morality in us...)

This is of course making use of the premise that reality is indivisible/simple..