I will prove to you that God exists

[GrandizerII]

Occams razor isn't about simplicity, its about unnecessarily multiplying entities.

Occam's razor is tied to simplicity, though. It's basically the principle of parsimony, which is simplicity. And people have debates about what sort of "simplicity" is relevant here. The more important point, however, is that a multiverse may be necessary because of something tied to the principle of sufficient reason ... or the principle of plenitude or something else. As such, not a butchering of Occam's razor.

Also, people subscribe to a multiverse view for various rational reasons, and not because they need it to explain something like the assumed "fine-tuning" of this local universe. Even some theists have argued for a multiverse view in favour of God because of things like the principle of sufficient reason.

There are other reasons such as the double slit experiment which gives rise to the idea every decision leads to a new universe. There are reasons to think cosmic inflation occurred and some theorize that process goes on to create other universes. Or that our universe includes pocket universes in which there are different laws of physics. No matter how you slice it along with it comes the explanation for fine-tuning of the universe. Its is part and parcel with the theory of multiverse. They almost act like fine-tuning is evidence of other universes...its not. The fine-tuning of this universe didn't cause other universes to exist. The best evidence of other universes is the existence of this one and we observe things in multiples all the time such as other galaxies.

Neither the double slit experiment or cosmic inflation support the idea of a multiverse directly, so your first two sentences here are iffy. Pocket universes aren't reasons but features that are posited or concluded. That said, some scientists do argue for some multiverse or another by appealing to observations made in quantum physics and cosmology, but atheists are allowed to resort to pure reason to argue for what's more likely (just as much as theists like to do). You gave one fair argument for a multiverse in your last sentence here. It seems like if we have multiple planets, multiple solar systems, multiple galaxies, maybe we also have multiple local universes. If you then add other reasons to accept a multiverse, you might come up with something compelling.

As for "fine-tuning", this is just an assumption, not an observed fact. A multiverse theory need not accept such an assumption, and it certainly doesn't need to explain it.

AI says...
The multiverse theory, which posits the existence of many universes with varying physical laws and constants, is often proposed as a naturalistic explanation for the apparent "fine-tuning" of our universe, suggesting that life-supporting conditions are merely a result of us inhabiting a universe that happens to be conducive to life. However, some argue that the multiverse itself requires fine-tuning, thus potentially undermining its explanatory power. 

Not concerned with what some random people argue regarding what the multiverse requires. There are different positions on the multiverse (just like there are different positions on God), and certainly not all of them require fine-tuning. For example, under a "modal realism" kind of multiverse, there is no fine-tuning. All worlds, including this world, simply are.

There is no direct evidence of God either, so we're even.

That's right. So it goes back to what we do know a universe came into existence that was able to cause intelligent life to exist. Scientists know a host of improbable events, properties and circumstances obtained for a life happy planet like earth to exist.

Scientists also know a host of probable accounts that are preferred over improbable ones, and they adequately account for the many observations we have made on our planet and in this local universe. The theory of evolution being one such account. Another is relativity.

When folks say we owe the existence of the universe to natural causes they can't mean the natural forces we're familiar with in space-time. Those natural forces are what came into existence. I assume they just mean other forces that unintentionally came into existence and unintentionally caused a universe to exist and had no intention of causing intelligent life to exist.

Or the universe has always been. And intention is something only us limited beings require.

That's a very tall drink of water and that's why even non-religious people think our existence was intentionally caused. Including a lot of scientists.

Name one.

The multiverse is just as much about "chance" as God is. Is God "chance"? Nope? Then good luck arguing the multiverse (without God) is any different in this case.

Its not about chances which are incalculable, its about what explanation explains best. Most atheists I run into deny there is a need for multiverse.

Most atheists (that you have encountered) prefer to be minimalistic in their approach to the big ontological questions regarding existence and the universe and such. For them, a multiverse is not needed, but neither is God.

But then again, your response is to me, not them. And I'm a multiverse guy.