Why did originate the protoplanet hypothesis based on theory?

The protoplanet hypothesis originated from the need to explain the formation of planets in a systematic way, based on observations of protoplanetary disks around young stars. It suggests that dust and gas in these disks coalesce through processes like accretion and gravitational attraction, leading to the formation of larger bodies, or protoplanets. This hypothesis is supported by the laws of physics, including gravity and conservation of angular momentum, and aligns with the observed structure of our solar system and others. Ultimately, it provides a coherent framework for understanding the transition from dust clouds to planetary systems.