Because there is. What is, IS.
The following is a layman’s explanation. It’s not perfect but you’ll get the idea.
So what IS?
Start with an energy field – for example imagine a large magnetic field- which you can’t feel or hold by itself (I don’t mean holding the magnet, just the field). The field is made up of massless photons.
Because massless photons can interact with a Higgs field they can gain inertia and become what we sense as solid matter- but solid matter is still just a different form of energy.
If you want to know the particulars you can read about it here:
If you don’t believe in a multiverse then the following argument might appear to be utter nonsense.
BUT if you DO believe in a multiverse- and I do believe in a multiverse- as do most cosmologists and theoretical physicists today- there are an infinite number of possible outcomes- because the multiverse has an infinite number of ways the laws of physics can be constructed.
Some might have laws that seem so foreign as to be incomprehensible to us, at least at our current state of knowledge and awareness. In some universe nothing might form at all.
It is true that particles can pop in and out of existence – they can exist physically and then not. It is still believed that within our universe there are a finite number of particles thought to be about 10 to the 80th power.
IF this is true, then those particles can be arranged and rearranged only so many ways. It is a very large number, but still a finite number.
After you have rearranged them in every possible way, and you arrange them one more time, you must come up with a duplicate arrangement.
Physicists believe this is true as a property of a universe.
Because of this, it is believed that in an infinite number of universes, in the multiverse, one of those rearrangements would look like you.
At some point you end up with you living on a planet that looks like earth.
And again with you on an earth going around a sun with planets that look like the ones in our solar system.
And how about you and earth and the solar system and New York City in the United States along with your best friend and your dog and your old significant other. You get the idea.
One of them is an exact repeat of our own universe. But in an infinite number of universes you end up with an infinite number of repeats. ZOUNDS!
Now here’s a great question for discussion: could your particles here somehow be entangled with the other you(s) there so that after you die here, you are still alive there. A scientific life after death? I am not aware of my other selves. But does that diminish their existence? No, it does not.
So the answer to the question asked is that we live in one of those universes where stuff happened rather than not. What we experience is the familiar. It seems amazing. It is amazing. But it is a mathematical probability that if it wasn’t you or me it would be someone else just as amazed living in their universe wondering the same thing.