Sachkandh is where the Bhagats brahmgyanis Gurus Sants who practice truth reside. When a soul there stops practicing and serving Truth, they no longer vibrate at the required frequency and are sent to lower realms.
The frequency you vibrate at depends on your truth practice, the less u practice, the lower your vibration. We all go to the level we belong at.
On earth, our frequency and vibration determines which realm we connect with, whether it be a heaven or a hell realm. Hence you can live heaven on earth or hell on earth.
In the age of Kalyug, the psychology has more or less become collective due to people's attachment to each other and BS society. The collective psychology has become hell on earth where the majority of the population live a hellish psychology. It is truly the blind leading the blind.
People live in maya I.e jealousy and envy of each other, lust of each other, attachment to each other, ego and anger and selfish pride and greed. People slander backstab and fight with each other. People will act good to each other and gossip and act in maya behind closed doors.
When you become a societal outcaste, shunning the expectations of society and you stop reacting in maya and start being positive and truthful, ie applying Gurbani to your life 100%, you detach from the rubbish and detach from the negativity and lift your vibration.
It takes one star to light up the sky which is why Gurbani tell us to follow the Satguru. The teachings of Gurbani/ Guru are the light of this age and applying it 100% we are able to release the bonds of societal BS and live in our True state.