Here's why:
* Gravitational Collapse: The Sun formed at the center of the protoplanetary disk through gravitational collapse. This process drew in the vast majority of the gas and dust from the surrounding disk.
* Mass Ratio: The Sun accounts for over 99.8% of the mass of our entire solar system. This means the remaining planets, moons, asteroids, and other objects only represent a tiny fraction of the original disk's material.
* Solar Wind: The Sun's powerful solar wind also played a role in pushing lighter elements like hydrogen and helium away from the inner solar system, further contributing to the Sun's mass dominance.
While the Sun is the dominant recipient of the disk's material, it's important to remember that the remaining portion is still significant. It formed everything else in our solar system, from the rocky planets to the icy outer bodies like comets.
