Did the Prophet, peace and blessings be upon him, command an increase in digging trenches to seek protection from a heavenly light that kills humans?

This statement has no basis. The Prophet, peace and blessings be upon him, only commanded the digging of one trench during the Battle of Al-Ahzab. The Rightly Guided Caliphs were not known to have done this, nor did scholars encourage it. Moreover, the appearance of light from the sky that kills people is a myth resembling the words of soothsayers. It is known that digging many trenches and fortifying positions within a country falls under the policies and plans of warfare, not religious matters.