How are lonely planets formed?

When two gravitating objects collide, or when these planets come too close to another planet orbiting the star, the planets deviate from their orbits and start traveling through space. Scientists believe that most of the lonely planets were formed in this way.
But another reason is that the star itself pushes the planet out of the planetary system. Basically, when a star goes supernova in its final state, the planets around it are ejected and hurtle aimlessly through space. This lonely planet then became saturated with its own gas and dust.
This is how Rogue Planet was created. However, some dwarf stars also roam alone in space. They are called solitary stars.