To expand:
The first cause argument argues for just that - a first cause (uncaused, independent).
These describe in part what Christians (and Acquinas) identify as God; however, the argument does not rely or require it. Again, that is one of the reasons used against it as it is used in making the “case for God.”
Why God created - beyond this logical argument - is in the area of theology, which would be a category error in our discussion. I’m sticking to the non-transcendent here.
But it's silly. The necessary logical conclusion is that first cause is without cause, or "just because," for no reason whatsoever.
Any reason given destroys the first cause. Why did first cause create the world? Just because. You can't say "because he so loved the world." That means the uncaused was caused to move by love. You can't say first cause "is" in order to be the first cause. In both instances you appealing to higher necessity that cause the "uncaused" to be or to create, and that destroyed the first cause argument.
This is where so many theologians run aground. Eventually they begin to subject even God to a higher necessity ("God had to..."), and we are right back to infinite regress.
If it is at the limit of logic, maybe we should just say it's an unreoslved paradox and we don't knwo the answer.