The peculiar thing is, although Zen sounds really stoic and far-fetched from ordinary people’s ordinary lives (which are filled with desire and lust), they were not secluded from society in Japan. They were instead respected and sought for their intellectual wealth and their ability to control/maintain mental stability.
This is the era (around 11th~ 14th century) where the power was shifting from aristocrats (Tenno or Emperor) to military (Sho-gun). Military power was rapidly taking control of the entire country and accumulating wealth that the society had never seen before. However, unprecedented accumulation of wealth resulted in unprecedented level of conflicts. The fights among regional powers intensified and peoples’ lives were devastated.
People were faced with a bitter realization: wealth is a source of pleasure, but it can cause devastating tragedy when people start fighting for it (and they always do). If you are in power you always have to be prepared for warfare and death. If you are a citizen you have to prepare for social unrest and destruction. People were torn apart between the pleasure of wealth and the tragedy it caused.
They needed Buddhism to overcome the enormous stress and despair. Zen monks were the go-to mentors in order to maintain a peace of mind despite harsh reality.
Torn apart between pleasure and tragedy, Zen monks accelerated their concentration training to get away from desire , the sources of tragedy.
Remember, Zen denies text.
Ultimately, many prominent monks crystallized their internal breakthroughs (to extinguish the flame of desire) as the abstract of various arts. One of the most famous artistic materialization of Zero is Kare-sansui, the Zen rock garden.
Ryoan Ji, Kyoto zen garden, By Cquest (Own work) [CC BY-SA 2.5], via Wikimedia Commons
For the Zen monks, “Zero” meant drastically reducing the amount of desire and pleasure. At the culmination of their Zero journey emerged beauty.
The crystallization of Zero was not nothingness.
They discovered that Zero was abundance.