I don't believe that anyone can ever know what caused the Universe. From a physical point of view it seems obvious to me that the Big Bang acts as some kind of barrier, disconnecting the Universe we can understand from whatever came "before" it; although it is possibly wrong to even assume that there was such a thing as "before": "what came before the Big Bang?" may be as meaningless a question as "what is North of the North Pole?"
But let's set all that aside. What "God" is, in TheLand's definition, is a first cause, a self-causing cause. Therefore, a thing that is capable of causing itself must exist. There is nothing in any of his posts to explain, or even come close to explaining, what property the Universe lacks that stops it from causing itself. It's not difficult to understand *why* he hasn't explained it, as it's the same reason he can't say why "God" has it, because he doesn't know what "it" is. This is not a criticism per se -- why should anyone be able to know what this is? -- but what it *does* mean is that the argument cannot possibly be persuasive.
All TheLand's argument really leads to is that there must exist something that is capable of creating itself. Why not the Universe? This has the benefit of being a simpler argument, because it posits the existence of one fewer entity in order to explain things. But, more than that, it has the benefit of being, potentially, a falsifiable argument. We will, I hope, never be able fully to understand all the mysteries of the Universe, but we can at least hope to be able to *try* and understand them, and to make progress because of that effort.
Understanding the possibility of life elsewhere would clearly be a part of that step. I can see why TheLand is, in essence, "scared" of the possibility, hence his dismissal of it, but that's unforgivably close-minded and incurious. Either there exists life beyond this planet or there does not, and either answer is equally amazing in its own way. It's disappointing that anyone wouldn't want to know, or has already made up their mind that there can be no such life.