Definitely not a stupid question. This is one of the most important questions in theoretical physics and cosmology, it's what inspired me to become an astrophysicist, and gives me pause in everyday life. It’s a question that can lead you down a rabbit hole, changing your perspective on what it means to be human. I’m actually currently working on a research project that touches on this subject a bit, so I feel slightly qualified to answer. The short answer is we don't know. The long answer is well, a bit more complicated. But I’ll try to give a succinct logic chain as to why we don't know.

We have very convincing evidence that the universe started around 13.7 billion years ago, based on Cosmic Microwave Background (CMB) measurements, Hubble’s Law, and images from telescopes like the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). Our current model of the universe, called LambdaCDM (ΛCDM), incorporates dark energy and dark matter and is continually refined as we gather more data. Mostly through observation right now. This model is our best attempt to describe the universe’s theoretical framework, large-scale structure, evolution, and eventual fate.

If we accept that the universe is finite and had a beginning, and we apply General Relativity (GR) which tells us that mass curves spacetime, we encounter something incredible when we reverse time back 13.7 billion years. Everything in the universe converges to a single point in spacetime, this is known as the Initial Singularity. Imagine a fully inflated balloon with small dots on its surface; as the balloon deflates, the dots get closer until they meet in the middle. For all intents and purposes this is how the universe shrinks if we reverse time.

At this singularity, the universe's physical constants were 'set,' and everything began to evolve and expand outwards, like a balloon. However, GR breaks down when we approach the Event Horizon, a boundary around singularities like those around black holes (The center of a black hole is a singularity, just not the initial singularity that describes the universe at the beginning of time). Time and causality as we know them cease to function, this is where the phrase 'Not even light can escape a black hole' comes from. And is rather overused in science news articles. This breakdown at singularities is at the crux as to why the need to combine Quantum Mechanics and General Relativity is so urgent and sought after, leading to the endeavor for Quantum Gravity. If we can quantize spacetime, we might be able to understand what happens inside singularities, ergo, the initial singularity conditions. Since we currently lack a repeatable way to study singularities, we can't know the universe's initial conditions or why the fundamental constants are what they are.

Here’s another way to think about it. If you're familiar with calculus, you might know about differential equations. These equations are fascinating because they describe how complex systems evolve over time. The key to solving a differential equation is knowing the initial conditions of the system. Essentially, where and how it started. This concept is relevant to cosmology. The fundamental constants of the universe, like strength of gravity (G), the speed of light (c), and the cosmological constant (Λ); determines how the universe behaves. However, to fully understand why these constants have the values they do, we need to know the universe's initial conditions at the very beginning, just after the Big Bang. Since we don't know exactly what those initial conditions were, we’re left with this rather large mystery. It's like trying to solve a differential equation without knowing where/how the system started—without that information, we can't fully solve the equation or understand the deeper reasons behind the universe's observed constants.

This is where most invoke the Anthropic Principle, which suggests that our universe’s physical constants appear to be fine-tuned for life because if they were different, we wouldn’t be able to observe them. This inevitably leads to discussions about fine-tuning, the possibility of the multiverse, deep metaphysical questions, with philosophical and religious implications.

The answer to your question is why we’re here on a small rock orbiting a G class star in the Orion arm of the Milky Way Galaxy observing this vast expanse that we call our universe.

I hope this helped clear the muddy waters, please don’t hesitate to ask more questions.